py: Convert mp_uint_t to size_t for tuple/list accessors.

This patch changes mp_uint_t to size_t for the len argument of the
following public facing C functions:

mp_obj_tuple_get
mp_obj_list_get
mp_obj_get_array

These functions take a pointer to the len argument (to be filled in by the
function) and callers of these functions should update their code so the
type of len is changed to size_t.  For ports that don't use nan-boxing
there should be no change in generate code because the size of the type
remains the same (word sized), and in a lot of cases there won't even be a
compiler warning if the type remains as mp_uint_t.

The reason for this change is to standardise on the use of size_t for
variables that count memory (or memory related) sizes/lengths.  It helps
builds that use nan-boxing.
diff --git a/py/builtinimport.c b/py/builtinimport.c
index 17c1622..8101d63 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -97,7 +97,7 @@
 STATIC mp_import_stat_t find_file(const char *file_str, uint file_len, vstr_t *dest) {
 #if MICROPY_PY_SYS
     // extract the list of paths
-    mp_uint_t path_num;
+    size_t path_num;
     mp_obj_t *path_items;
     mp_obj_list_get(mp_sys_path, &path_num, &path_items);
 
diff --git a/py/modthread.c b/py/modthread.c
index ecf4705..d0e71da 100644
--- a/py/modthread.c
+++ b/py/modthread.c
@@ -215,7 +215,7 @@
     thread_entry_args_t *th_args;
 
     // get positional arguments
-    mp_uint_t pos_args_len;
+    size_t pos_args_len;
     mp_obj_t *pos_args_items;
     mp_obj_get_array(args[1], &pos_args_len, &pos_args_items);
 
diff --git a/py/obj.c b/py/obj.c
index 4b5fe25..98ffa93 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -321,7 +321,7 @@
 #endif
 
 // note: returned value in *items may point to the interior of a GC block
-void mp_obj_get_array(mp_obj_t o, mp_uint_t *len, mp_obj_t **items) {
+void mp_obj_get_array(mp_obj_t o, size_t *len, mp_obj_t **items) {
     if (MP_OBJ_IS_TYPE(o, &mp_type_tuple)) {
         mp_obj_tuple_get(o, len, items);
     } else if (MP_OBJ_IS_TYPE(o, &mp_type_list)) {
@@ -338,7 +338,7 @@
 
 // note: returned value in *items may point to the interior of a GC block
 void mp_obj_get_array_fixed_n(mp_obj_t o, size_t len, mp_obj_t **items) {
-    mp_uint_t seq_len;
+    size_t seq_len;
     mp_obj_get_array(o, &seq_len, items);
     if (seq_len != len) {
         if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
diff --git a/py/obj.h b/py/obj.h
index 71945f4..65543b7 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -676,7 +676,7 @@
 void mp_obj_get_complex(mp_obj_t self_in, mp_float_t *real, mp_float_t *imag);
 #endif
 //qstr mp_obj_get_qstr(mp_obj_t arg);
-void mp_obj_get_array(mp_obj_t o, mp_uint_t *len, mp_obj_t **items); // *items may point inside a GC block
+void mp_obj_get_array(mp_obj_t o, size_t *len, mp_obj_t **items); // *items may point inside a GC block
 void mp_obj_get_array_fixed_n(mp_obj_t o, size_t len, mp_obj_t **items); // *items may point inside a GC block
 size_t mp_get_index(const mp_obj_type_t *type, size_t len, mp_obj_t index, bool is_slice);
 mp_obj_t mp_obj_id(mp_obj_t o_in);
@@ -728,7 +728,7 @@
 #endif
 
 // tuple
-void mp_obj_tuple_get(mp_obj_t self_in, mp_uint_t *len, mp_obj_t **items);
+void mp_obj_tuple_get(mp_obj_t self_in, size_t *len, mp_obj_t **items);
 void mp_obj_tuple_del(mp_obj_t self_in);
 mp_int_t mp_obj_tuple_hash(mp_obj_t self_in);
 
@@ -737,7 +737,7 @@
 void mp_obj_list_init(struct _mp_obj_list_t *o, size_t n);
 mp_obj_t mp_obj_list_append(mp_obj_t self_in, mp_obj_t arg);
 mp_obj_t mp_obj_list_remove(mp_obj_t self_in, mp_obj_t value);
-void mp_obj_list_get(mp_obj_t self_in, mp_uint_t *len, mp_obj_t **items);
+void mp_obj_list_get(mp_obj_t self_in, size_t *len, mp_obj_t **items);
 void mp_obj_list_set_len(mp_obj_t self_in, size_t len);
 void mp_obj_list_store(mp_obj_t self_in, mp_obj_t index, mp_obj_t value);
 mp_obj_t mp_obj_list_sort(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs);
diff --git a/py/objfun.c b/py/objfun.c
index 4670521..2ce33cb 100644
--- a/py/objfun.c
+++ b/py/objfun.c
@@ -513,7 +513,7 @@
 #endif
         } else if (type == &mp_type_tuple || type == &mp_type_list) {
             // pointer to start of tuple (could pass length, but then could use len(x) for that)
-            mp_uint_t len;
+            size_t len;
             mp_obj_t *items;
             mp_obj_get_array(obj, &len, &items);
             return (mp_uint_t)items;
diff --git a/py/objlist.c b/py/objlist.c
index 312cef6..45e69c8 100644
--- a/py/objlist.c
+++ b/py/objlist.c
@@ -192,7 +192,7 @@
 #if MICROPY_PY_BUILTINS_SLICE
         if (MP_OBJ_IS_TYPE(index, &mp_type_slice)) {
             mp_obj_list_t *self = MP_OBJ_TO_PTR(self_in);
-            mp_uint_t value_len; mp_obj_t *value_items;
+            size_t value_len; mp_obj_t *value_items;
             mp_obj_get_array(value, &value_len, &value_items);
             mp_bound_slice_t slice_out;
             if (!mp_seq_get_fast_slice_indexes(self->len, index, &slice_out)) {
@@ -475,7 +475,7 @@
     return MP_OBJ_FROM_PTR(o);
 }
 
-void mp_obj_list_get(mp_obj_t self_in, mp_uint_t *len, mp_obj_t **items) {
+void mp_obj_list_get(mp_obj_t self_in, size_t *len, mp_obj_t **items) {
     mp_obj_list_t *self = MP_OBJ_TO_PTR(self_in);
     *len = self->len;
     *items = self->items;
diff --git a/py/objnamedtuple.c b/py/objnamedtuple.c
index 2371518..5246874 100644
--- a/py/objnamedtuple.c
+++ b/py/objnamedtuple.c
@@ -158,7 +158,7 @@
 
 STATIC mp_obj_t new_namedtuple_type(mp_obj_t name_in, mp_obj_t fields_in) {
     qstr name = mp_obj_str_get_qstr(name_in);
-    mp_uint_t n_fields;
+    size_t n_fields;
     mp_obj_t *fields;
     #if MICROPY_CPYTHON_COMPAT
     if (MP_OBJ_IS_STR(fields_in)) {
diff --git a/py/objstr.c b/py/objstr.c
index 4053efb..682bd26 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -284,7 +284,7 @@
     // check for modulo
     if (op == MP_BINARY_OP_MODULO) {
         mp_obj_t *args = &rhs_in;
-        mp_uint_t n_args = 1;
+        size_t n_args = 1;
         mp_obj_t dict = MP_OBJ_NULL;
         if (MP_OBJ_IS_TYPE(rhs_in, &mp_type_tuple)) {
             // TODO: Support tuple subclasses?
@@ -428,7 +428,7 @@
     GET_STR_DATA_LEN(self_in, sep_str, sep_len);
 
     // process args
-    mp_uint_t seq_len;
+    size_t seq_len;
     mp_obj_t *seq_items;
 
     if (!MP_OBJ_IS_TYPE(arg, &mp_type_list) && !MP_OBJ_IS_TYPE(arg, &mp_type_tuple)) {
diff --git a/py/objtuple.c b/py/objtuple.c
index a8efdc7..fa5309a 100644
--- a/py/objtuple.c
+++ b/py/objtuple.c
@@ -244,7 +244,7 @@
     return MP_OBJ_FROM_PTR(o);
 }
 
-void mp_obj_tuple_get(mp_obj_t self_in, mp_uint_t *len, mp_obj_t **items) {
+void mp_obj_tuple_get(mp_obj_t self_in, size_t *len, mp_obj_t **items) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_tuple));
     mp_obj_tuple_t *self = MP_OBJ_TO_PTR(self_in);
     *len = self->len;
diff --git a/py/objtype.c b/py/objtype.c
index a64832c..dd170b4 100644
--- a/py/objtype.c
+++ b/py/objtype.c
@@ -916,7 +916,7 @@
     // TODO might need to make a copy of locals_dict; at least that's how CPython does it
 
     // Basic validation of base classes
-    mp_uint_t len;
+    size_t len;
     mp_obj_t *items;
     mp_obj_tuple_get(bases_tuple, &len, &items);
     for (size_t i = 0; i < len; i++) {
@@ -1098,7 +1098,7 @@
 }
 
 STATIC mp_obj_t mp_obj_is_subclass(mp_obj_t object, mp_obj_t classinfo) {
-    mp_uint_t len;
+    size_t len;
     mp_obj_t *items;
     if (MP_OBJ_IS_TYPE(classinfo, &mp_type_type)) {
         len = 1;
diff --git a/py/runtime.c b/py/runtime.c
index 9f6c654..73886e1 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -670,7 +670,7 @@
         // optimise the case of a tuple and list
 
         // get the items
-        mp_uint_t len;
+        size_t len;
         mp_obj_t *items;
         mp_obj_get_array(pos_seq, &len, &items);
 
@@ -799,7 +799,7 @@
 
 // unpacked items are stored in reverse order into the array pointed to by items
 void mp_unpack_sequence(mp_obj_t seq_in, size_t num, mp_obj_t *items) {
-    mp_uint_t seq_len;
+    size_t seq_len;
     if (MP_OBJ_IS_TYPE(seq_in, &mp_type_tuple) || MP_OBJ_IS_TYPE(seq_in, &mp_type_list)) {
         mp_obj_t *seq_items;
         mp_obj_get_array(seq_in, &seq_len, &seq_items);
@@ -849,7 +849,7 @@
     size_t num_left = num_in & 0xff;
     size_t num_right = (num_in >> 8) & 0xff;
     DEBUG_OP_printf("unpack ex " UINT_FMT " " UINT_FMT "\n", num_left, num_right);
-    mp_uint_t seq_len;
+    size_t seq_len;
     if (MP_OBJ_IS_TYPE(seq_in, &mp_type_tuple) || MP_OBJ_IS_TYPE(seq_in, &mp_type_list)) {
         mp_obj_t *seq_items;
         mp_obj_get_array(seq_in, &seq_len, &seq_items);