Unify event handling behavior for all cases

This makes the individual plugin host slightly more complex, but now
both individually hosted plugins and plugin groups handle both
dispatcher events and GUI events in the exact same way.

src/wine-host/bridges/group.h

@@ -176,7 +176,7 @@ class GroupBridge {
      * works, all plugins have to be initialized from the same thread, and all
      * event handling and message loop interaction also has to be done from that
      * thread, which is why we initialize the plugin here and use the
-     * `handle_dispatch_multi()` function to run events within the same
+     * `handle_dispatch()` function to run events within the same
      * `plugin_context`.
      *
      * @see handle_plugin_dispatch
@@ -185,8 +185,7 @@ class GroupBridge {
 
     /**
      * Handle both Win32 messages and X11 events on a timer within the IO
-     * context. This is a centralized replacement for the event handling in
-     * `Vst2Bridge::handle_dispatch_single` for plugin groups.
+     * context for all plugins.
      */
     void async_handle_events();