py: Add new cstack API for stack checking, with limit margin macro.

Currently the stack limit margin is hard-coded in each port's call to
`mp_stack_set_limit()`, but on threaded ports it's fiddlier and can lead to
bugs (such as incorrect thread stack margin on esp32).

This commit provides a new API to initialise the C Stack in one function
call, with a config macro to set the margin.  Where possible the new call
is inlined to reduce code size in thread-free ports.

Intended replacement for `MP_TASK_STACK_LIMIT_MARGIN` on esp32.

The previous `stackctrl.h` API is still present and unmodified apart from a
deprecation comment.  However it's not available when the
`MICROPY_PREVIEW_VERSION_2` macro is set.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

py/objlist.c

@@ -29,7 +29,7 @@
 
 #include "py/objlist.h"
 #include "py/runtime.h"
-#include "py/stackctrl.h"
+#include "py/cstack.h"
 
 static mp_obj_t mp_obj_new_list_iterator(mp_obj_t list, size_t cur, mp_obj_iter_buf_t *iter_buf);
 static mp_obj_list_t *list_new(size_t n);
@@ -291,7 +291,7 @@ static mp_obj_t list_pop(size_t n_args, const mp_obj_t *args) {
 }
 
 static void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn, mp_obj_t binop_less_result) {
-    MP_STACK_CHECK();
+    mp_cstack_check();
     while (head < tail) {
         mp_obj_t *h = head - 1;
         mp_obj_t *t = tail;