py/mphal: Move configuration of ATOMIC_SECTION macros to mphal.h.

MICROPY_BEGIN_ATOMIC_SECTION/MICROPY_END_ATOMIC_SECTION belong more to the
MicroPython HAL rather than build configuration settings, so move their
default configuration to py/mphal.h, and require all users of these macros
to include py/mphal.h (here, py/objexcept.c and py/scheduler.c).

This helps ports separate configuration from their HAL implementations, and
can improve build times (because mpconfig.h is included everywhere, whereas
mphal.h is not).
Signed-off-by: Damien George <damien@micropython.org>

py/mpconfig.h

@@ -1850,14 +1850,6 @@ typedef double mp_float_t;
 #endif
 #endif
 
-// On embedded platforms, these will typically enable/disable irqs.
-#ifndef MICROPY_BEGIN_ATOMIC_SECTION
-#define MICROPY_BEGIN_ATOMIC_SECTION() (0)
-#endif
-#ifndef MICROPY_END_ATOMIC_SECTION
-#define MICROPY_END_ATOMIC_SECTION(state) (void)(state)
-#endif
-
 // Allow to override static modifier for global objects, e.g. to use with
 // object code analysis tools which don't support static symbols.
 #ifndef STATIC

py/mphal.h

@@ -35,6 +35,14 @@
 #include <mphalport.h>
 #endif
 
+// On embedded platforms, these will typically enable/disable irqs.
+#ifndef MICROPY_BEGIN_ATOMIC_SECTION
+#define MICROPY_BEGIN_ATOMIC_SECTION() (0)
+#endif
+#ifndef MICROPY_END_ATOMIC_SECTION
+#define MICROPY_END_ATOMIC_SECTION(state) (void)(state)
+#endif
+
 #ifndef mp_hal_stdio_poll
 uintptr_t mp_hal_stdio_poll(uintptr_t poll_flags);
 #endif

py/objexcept.c

@@ -81,6 +81,8 @@ void mp_init_emergency_exception_buf(void) {
 #else
 #define mp_emergency_exception_buf_size MP_STATE_VM(mp_emergency_exception_buf_size)
 
+#include "py/mphal.h" // for MICROPY_BEGIN_ATOMIC_SECTION/MICROPY_END_ATOMIC_SECTION
+
 void mp_init_emergency_exception_buf(void) {
     mp_emergency_exception_buf_size = 0;
     MP_STATE_VM(mp_emergency_exception_buf) = NULL;

py/scheduler.c

@@ -26,6 +26,7 @@
 
 #include <stdio.h>
 
+#include "py/mphal.h"
 #include "py/runtime.h"
 
 // Schedules an exception on the main thread (for exceptions "thrown" by async