py/obj: Merge getiter and iternext mp_obj_type_t slots.

The goal here is to remove a slot (making way to turn make_new into a slot)
as well as reduce code size by the ~40 references to mp_identity_getiter
and mp_stream_unbuffered_iter.

This introduces two new type flags:
- MP_TYPE_FLAG_ITER_IS_ITERNEXT: This means that the "iter" slot in the
  type is "iternext", and should use the identity getiter.
- MP_TYPE_FLAG_ITER_IS_CUSTOM: This means that the "iter" slot is a pointer
  to a mp_getiter_iternext_custom_t instance, which then defines both
  getiter and iternext.

And a third flag that is the OR of both, MP_TYPE_FLAG_ITER_IS_STREAM: This
means that the type should use the identity getiter, and
mp_stream_unbuffered_iter as iternext.

Finally, MP_TYPE_FLAG_ITER_IS_GETITER is defined as a no-op flag to give
the default case where "iter" is "getiter".

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/nrf/boards/microbit/modules/iters.c

@@ -46,10 +46,9 @@ static mp_obj_t microbit_repeat_iter_next(mp_obj_t iter_in) {
 MP_DEFINE_CONST_OBJ_TYPE(
     microbit_repeat_iterator_type,
     MP_QSTR_iterator,
-    MP_TYPE_FLAG_NONE,
+    MP_TYPE_FLAG_ITER_IS_ITERNEXT,
     MP_TYPE_NULL_MAKE_NEW,
-    getiter, mp_identity_getiter,
-    iternext, microbit_repeat_iter_next
+    iter, microbit_repeat_iter_next
     );
 
 mp_obj_t microbit_repeat_iterator(mp_obj_t iterable) {

ports/nrf/boards/microbit/modules/microbitimage.c

@@ -824,18 +824,16 @@ STATIC mp_obj_t microbit_scrolling_string_iter_next(mp_obj_t o_in) {
 MP_DEFINE_CONST_OBJ_TYPE(
     microbit_scrolling_string_type,
     MP_QSTR_ScrollingString,
-    MP_TYPE_FLAG_NONE,
-    MP_TYPE_NULL_MAKE_NEW,
-    getiter, get_microbit_scrolling_string_iter
+    MP_TYPE_FLAG_ITER_IS_GETITER,
+    iter, get_microbit_scrolling_string_iter
     );
 
 MP_DEFINE_CONST_OBJ_TYPE(
     microbit_scrolling_string_iterator_type,
     MP_QSTR_iterator,
-    MP_TYPE_FLAG_NONE,
+    MP_TYPE_FLAG_ITER_IS_ITERNEXT,
     MP_TYPE_NULL_MAKE_NEW,
-    getiter, mp_identity_getiter,
-    iternext, microbit_scrolling_string_iter_next
+    iter, microbit_scrolling_string_iter_next
     );
 
 /** Facade types to present a string as a sequence of images.
@@ -877,11 +875,10 @@ static mp_obj_t microbit_facade_iterator(mp_obj_t iterable_in, mp_obj_iter_buf_t
 MP_DEFINE_CONST_OBJ_TYPE(
     string_image_facade_type,
     MP_QSTR_Facade,
-    MP_TYPE_FLAG_NONE,
-    MP_TYPE_NULL_MAKE_NEW,
+    MP_TYPE_FLAG_ITER_IS_GETITER,
     unary_op, facade_unary_op,
     subscr, string_image_facade_subscr,
-    getiter, microbit_facade_iterator
+    iter, microbit_facade_iterator
     );
 
 
@@ -914,10 +911,9 @@ static mp_obj_t microbit_facade_iter_next(mp_obj_t iter_in) {
 MP_DEFINE_CONST_OBJ_TYPE(
     microbit_facade_iterator_type,
     MP_QSTR_iterator,
-    MP_TYPE_FLAG_NONE,
+    MP_TYPE_FLAG_ITER_IS_ITERNEXT,
     MP_TYPE_NULL_MAKE_NEW,
-    getiter, mp_identity_getiter,
-    iternext, microbit_facade_iter_next
+    iter, microbit_facade_iter_next
     );
 
 mp_obj_t microbit_facade_iterator(mp_obj_t iterable_in, mp_obj_iter_buf_t *iter_buf) {

ports/nrf/modules/machine/uart.c

@@ -373,11 +373,9 @@ STATIC const mp_stream_p_t uart_stream_p = {
 MP_DEFINE_CONST_OBJ_TYPE(
     machine_hard_uart_type,
     MP_QSTR_UART,
-    MP_TYPE_FLAG_NONE,
+    MP_TYPE_FLAG_ITER_IS_STREAM,
     machine_hard_uart_make_new,
     print, machine_hard_uart_print,
-    getiter, mp_identity_getiter,
-    iternext, mp_stream_unbuffered_iter,
     protocol, &uart_stream_p,
     locals_dict, &machine_hard_uart_locals_dict
     );