Remove mp_obj_type_t.methods entry and use .locals_dict instead.

Originally, .methods was used for methods in a ROM class, and
locals_dict for methods in a user-created class.  That distinction is
unnecessary, and we can use locals_dict for ROM classes now that we have
ROMable maps.

This removes an entry in the bloated mp_obj_type_t struct, saving a word
for each ROM object and each RAM object.  ROM objects that have a
methods table (now a locals_dict) need an extra word in total (removed
the methods pointer (1 word), no longer need the sentinel (2 words), but
now need an mp_obj_dict_t wrapper (4 words)).  But RAM objects save a
word because they never used the methods entry.

Overall the ROM usage is down by a few hundred bytes, and RAM usage is
down 1 word per user-defined type/class.

There is less code (no need to check 2 tables), and now consistent with
the way ROM modules have their tables initialised.

Efficiency is very close to equivaluent.

1 files changed, 8 insertions, 6 deletions

diff --git a/stm/pin.c b/stm/pin.c
index 4bdbfcb16b..6b97d2f7c1 100644
--- a/stm/pin.c
+++ b/stm/pin.c
@@ -7,6 +7,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 
 #include "pin.h"
 
@@ -34,18 +35,19 @@ static MP_DEFINE_CONST_FUN_OBJ_1(pin_obj_name_obj, pin_obj_name);
 static MP_DEFINE_CONST_FUN_OBJ_1(pin_obj_port_obj, pin_obj_port);
 static MP_DEFINE_CONST_FUN_OBJ_1(pin_obj_pin_obj, pin_obj_pin);
 
-static const mp_method_t pin_methods[] = {
-    { MP_QSTR_name, &pin_obj_name_obj },
-    { MP_QSTR_port, &pin_obj_port_obj },
-    { MP_QSTR_pin, &pin_obj_pin_obj },
-    { MP_QSTR_NULL, NULL },
+STATIC const mp_map_elem_t pin_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_name), (mp_obj_t)&pin_obj_name_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_port), (mp_obj_t)&pin_obj_port_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_pin), (mp_obj_t)&pin_obj_pin_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(pin_locals_dict, pin_locals_dict_table);
+
 const mp_obj_type_t pin_obj_type = {
     { &mp_type_type },
     .name = MP_QSTR_Pin,
     .print = pin_obj_print,
-    .methods = pin_methods,
+    .locals_dict = (mp_obj_t)&pin_locals_dict,
 };
 
 void pin_af_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {