mpconfig: Use RUN_BACKGROUND_TASKS as the micropython event hook

This is a newer abstraction in micropython; it'll for instance
allow background tasks to be checked once per ms in the internal
select module modselect.

Because `MICROPY_INTERNAL_EVENT_HOOK` is used in a few locations,
our own CIRCUITPY-CHANGE call to `RUN_BACKGROUND_TASKS` can be
nixed. Specifically, `mp_event_handle_nowait` calls
`MICROPY_INTERNAL_EVENT_HOOK` so paths from it don't need
`RUN_BACKGROUND_TASKS` anymore.

Author: jepler

py/circuitpy_mpconfig.h

@@ -452,6 +452,7 @@ void background_callback_run_all(void);
 
 #define MICROPY_VM_HOOK_LOOP RUN_BACKGROUND_TASKS;
 #define MICROPY_VM_HOOK_RETURN RUN_BACKGROUND_TASKS;
+#define MICROPY_INTERNAL_EVENT_HOOK (RUN_BACKGROUND_TASKS)
 
 // CIRCUITPY_AUTORELOAD_DELAY_MS = 0 will completely disable autoreload.
 #ifndef CIRCUITPY_AUTORELOAD_DELAY_MS

py/scheduler.c

@@ -271,10 +271,6 @@ void mp_event_wait_indefinite(void) {
     MICROPY_EVENT_POLL_HOOK
     #else
     mp_event_handle_nowait();
-
-    // CIRCUITPY-CHANGE: don't starve CircuitPython background tasks
-    RUN_BACKGROUND_TASKS;
-
     MICROPY_INTERNAL_WFE(-1);
     #endif
 }
@@ -287,10 +283,6 @@ void mp_event_wait_ms(mp_uint_t timeout_ms) {
     MICROPY_EVENT_POLL_HOOK
     #else
     mp_event_handle_nowait();
-
-    // CIRCUITPY-CHANGE: don't starve CircuitPython background tasks
-    RUN_BACKGROUND_TASKS;
-
     MICROPY_INTERNAL_WFE(timeout_ms);
     #endif
 }