py/scheduler: Add "raise_exc" argument to mp_handle_pending.

Previous behaviour is when this argument is set to "true", in which case
the function will raise any pending exception.  Setting it to "false" will
cancel any pending exception.
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 983c882..96e47fb 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -244,8 +244,8 @@
 #if MICROPY_PY_THREAD
 #define MICROPY_EVENT_POLL_HOOK \
     do { \
-        extern void mp_handle_pending(void); \
-        mp_handle_pending(); \
+        extern void mp_handle_pending(bool); \
+        mp_handle_pending(true); \
         MICROPY_PY_USOCKET_EVENTS_HANDLER \
         MP_THREAD_GIL_EXIT(); \
         MP_THREAD_GIL_ENTER(); \
@@ -253,8 +253,8 @@
 #else
 #define MICROPY_EVENT_POLL_HOOK \
     do { \
-        extern void mp_handle_pending(void); \
-        mp_handle_pending(); \
+        extern void mp_handle_pending(bool); \
+        mp_handle_pending(true); \
         MICROPY_PY_USOCKET_EVENTS_HANDLER \
         asm("waiti 0"); \
     } while (0);