[Keyboard] Fixes to make snes_macropad play nicer with qmk configurator (#22432)

* [Keyboard] Change default implementation for get_layer_name_user

Will now show the layer number instead of "Unknown", since this is
what will be shown if QMK Configurator is used to compile the
firmware.

* [Keyboard] Update the layout info

This makes it look sort of like a macropad + gamepad rather than an 4x6
ortholinear keyboard.

* [Keyboard] Fix default implementation of get_layer_name_user

Based on feedback from code review the implementation was swapped in
favor of using get_u8_str. This implied a change to the argument type
from int to uint8_t, which cascaded into the existing keymaps. (This
made sense in general, since the return type of get_highest_layer is
also a uint8_t.)

keyboards/snes_macropad/keymaps/default/keymap.c

@@ -61,7 +61,7 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 };
 // clang-format on
 
-const char* get_layer_name_user(int layer) {
+const char* get_layer_name_user(uint8_t layer) {
     switch (layer) {
         case L_Numpad:
             return "Numpad";