refactor(core): Move to stack allocated events.

* Move to local/stack allocated event API that doesn't require
  dynamic allocation/freeing.
* Disable heap, we no longer use alloc/free unless using LVGL.
* Tons of refactors all over to account for the new event approach.

app/src/event_manager.c

@@ -32,21 +32,17 @@ int zmk_event_manager_handle_from(zmk_event_t *event, uint8_t start_index) {
             continue;
         case ZMK_EV_EVENT_HANDLED:
             LOG_DBG("Listener handled the event");
-            ret = 0;
-            goto release;
+            return 0;
         case ZMK_EV_EVENT_CAPTURED:
             LOG_DBG("Listener captured the event");
-            // Listeners are expected to free events they capture
             return 0;
         default:
             LOG_DBG("Listener returned an error: %d", ret);
-            goto release;
+            return ret;
         }
     }
 
-release:
-    k_free(event);
-    return ret;
+    return 0;
 }
 
 int zmk_event_manager_raise(zmk_event_t *event) { return zmk_event_manager_handle_from(event, 0); }