Use callback-style events throughout all versions

Removes the need for //#if statements on each and every event handler.
Instead we now always use the equivalent Callback and have one central 1.12.2
class which forwards Forge events to the callbacks.

src/main/java/com/replaymod/replay/gui/overlay/GuiReplayOverlay.java

@@ -170,12 +170,7 @@ public class GuiReplayOverlay extends AbstractGuiOverlay<GuiReplayOverlay> {
         return this;
     }
 
-    //#if MC>=10800
-    private
-    //#else
-    //$$ public // All event handlers need to be public in 1.7.10
-    //#endif
-    class EventHandler extends EventRegistrations {
+    private class EventHandler extends EventRegistrations {
         { on(KeyBindingEventCallback.EVENT, this::onKeyBindingEvent); }
         private void onKeyBindingEvent() {
             GameOptions gameSettings = getMinecraft().options;