Simplify NIBBLE encoder code and clean up keymaps (#11808)

* Simplify encoder code and clean up keymaps.

-Removed overly complex VIA encoder code. It wasn't adding any value and was confusing users who were trying to customize encoder functionality on VIA keymaps.
-Replaced KC_TILDE with KC_HOME in all keymaps, as KC_TILDE sends a left shift, which was confusing some folks as they tested their build.
-Move layer names to enum

* Change encoder_update_kb to encoder_update_user per PR feedback

keyboards/nullbitsco/nibble/keymaps/iso/keymap.c

@@ -15,8 +15,10 @@
  */
 #include QMK_KEYBOARD_H
 
-#define _MA 0
-#define _FN 1
+enum layer_names {
+  _MA,
+  _FN
+};
 
 enum custom_keycodes {
   KC_CUST = SAFE_RANGE,
@@ -103,7 +105,7 @@ void change_RGB(bool clockwise) {
     }
 }
 
-void encoder_update_kb(uint8_t index, bool clockwise) {
+void encoder_update_user(uint8_t index, bool clockwise) {
   if (layer_state_is(1)) {
     //change RGB settings
     change_RGB(clockwise);