py: Protect mp_parse and mp_compile with nlr push/pop block.

To enable parsing constants more efficiently, mp_parse should be allowed
to raise an exception, and mp_compile can already raise a MemoryError.
So these functions need to be protected by an nlr push/pop block.

This patch adds that feature in all places.  This allows to simplify how
mp_parse and mp_compile are called: they now raise an exception if they
have an error and so explicit checking is not needed anymore.
diff --git a/py/compile.c b/py/compile.c
index 8e4723f..7023e9c 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -3823,7 +3823,7 @@
     m_del_obj(compiler_t, comp);
 
     if (compile_error != MP_OBJ_NULL) {
-        return compile_error;
+        nlr_raise(compile_error);
     } else {
 #if MICROPY_EMIT_CPYTHON
         // can't create code, so just return true