pybricks.parameters.Color: fix dictionary getting GCed

The colors dictionary was not accessible via root pointers and was
getting GCed.

This adds it to the root pointers.

Also allocate enough values for the color constants during init so that
we don't have to keep reallocating memory.

Fixes: pybricks/support#314

Author: dlech

bricks/ev3dev/mpconfigport.h

@@ -385,6 +385,7 @@ struct _mp_bluetooth_btstack_root_pointers_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
+    mp_obj_dict_t *pb_type_Color_dict; \
     const char *readline_hist[50]; \
     void *mmap_region_head; \
     MICROPY_BLUETOOTH_ROOT_POINTERS \

bricks/ev3rt/mpconfigport.h

@@ -96,6 +96,7 @@
     { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&mp_builtin_open_obj) },*/
 
 #define MICROPY_PORT_ROOT_POINTERS \
+    mp_obj_dict_t *pb_type_Color_dict; \
 
 //////////////////////////////////////////
 // Do not change anything beyond this line

bricks/nxt/mpconfigport.h

@@ -136,6 +136,7 @@ extern const struct _mp_obj_module_t pb_package_pybricks;
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
+    mp_obj_dict_t *pb_type_Color_dict; \
     const char *readline_hist[8];
 
 #include "../pybricks_config.h"

bricks/stm32/configport.h

@@ -163,6 +163,7 @@ static inline mp_uint_t disable_irq(void) {
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
+    mp_obj_dict_t *pb_type_Color_dict; \
     const char *readline_hist[8];
 
 #include "../pybricks_config.h"

pybricks/parameters/pb_type_color.c

@@ -117,12 +117,9 @@ static mp_obj_t pb_type_Color_make_new_helper(mp_int_t h, mp_int_t s, mp_int_t v
     return MP_OBJ_FROM_PTR(self);
 }
 
-// Create and reset dict to hold default colors and those added by user
-STATIC mp_obj_dict_t *colors;
-
 void pb_type_Color_reset(void) {
     // Set default contents of Color class
-    colors = mp_obj_new_dict(0);
+    mp_obj_dict_t *colors = mp_obj_new_dict(13);
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_RED),     MP_OBJ_FROM_PTR(&pb_Color_RED_obj));
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_BROWN),   MP_OBJ_FROM_PTR(&pb_Color_BROWN_obj));
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_ORANGE),  MP_OBJ_FROM_PTR(&pb_Color_ORANGE_obj));
@@ -136,19 +133,20 @@ void pb_type_Color_reset(void) {
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_GRAY),    MP_OBJ_FROM_PTR(&pb_Color_GRAY_obj));
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_WHITE),   MP_OBJ_FROM_PTR(&pb_Color_WHITE_obj));
     mp_obj_dict_store(MP_OBJ_FROM_PTR(colors), MP_ROM_QSTR(MP_QSTR_NONE),    MP_OBJ_FROM_PTR(&pb_Color_NONE_obj));
+    MP_STATE_VM(pb_type_Color_dict) = colors;
 }
 
 void pb_type_Color_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
 
     // If we're the class itself, use dict printer
     if (MP_OBJ_TO_PTR(self_in) == &pb_type_Color_obj) {
-        mp_type_dict.print(print, colors, kind);
+        mp_type_dict.print(print, MP_STATE_VM(pb_type_Color_dict), kind);
         return;
     }
 
     // Otherwise, print name of color, if available
-    mp_map_elem_t *color_elems = colors->map.table;
-    for (size_t i = 0; i < colors->map.alloc; i++) {
+    mp_map_elem_t *color_elems = MP_STATE_VM(pb_type_Color_dict)->map.table;
+    for (size_t i = 0; i < MP_STATE_VM(pb_type_Color_dict)->map.alloc; i++) {
         mp_map_elem_t *element = &color_elems[i];
         if (self_in == element->value && MP_OBJ_IS_QSTR(element->key)) {
             mp_printf(print, "Color.%q", MP_OBJ_QSTR_VALUE(element->key));
@@ -174,7 +172,7 @@ STATIC mp_obj_t pb_type_Color_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t
     }
 
     // Treat it like a dictionary
-    return mp_type_dict.subscr(colors, index, value);
+    return mp_type_dict.subscr(MP_STATE_VM(pb_type_Color_dict), index, value);
 }
 
 STATIC mp_obj_t pb_type_Color_getiter(mp_obj_t self_in, mp_obj_iter_buf_t *iter_buf) {
@@ -185,7 +183,7 @@ STATIC mp_obj_t pb_type_Color_getiter(mp_obj_t self_in, mp_obj_iter_buf_t *iter_
     }
 
     // Treat it like a dictionary
-    return mp_type_dict.getiter(colors, iter_buf);
+    return mp_type_dict.getiter(MP_STATE_VM(pb_type_Color_dict), iter_buf);
 }
 
 STATIC void pb_type_Color_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {