Rename GroupRequest to HostRequest

We'll also use this to encode information in when launching
`yabridge-host.exe` for individually hosted plugins.

src/wine-host/bridges/group.cpp

@@ -184,8 +184,8 @@ void GroupBridge::accept_requests() {
             // TODO: Do something with the plugin type
             // TODO: Maybe try to merge instantiation with `individual_host`?
             //       Might only make things messier
-            const auto request = read_object<GroupRequest>(socket);
-            write_object(socket, GroupResponse{boost::this_process::get_id()});
+            const auto request = read_object<HostRequest>(socket);
+            write_object(socket, HostResponse{boost::this_process::get_id()});
 
             // The plugin has to be initiated on the IO context's thread because
             // this has to be done on the same thread that's handling messages,

src/wine-host/bridges/vst2.h

@@ -68,7 +68,7 @@ class Vst2Bridge {
      *   or if communication could not be set up.
      *
      * TODO: Make these two arguments `boost::filesystem::path`, also use those
-     *       in `GroupRequest`.
+     *       in `HostRequest`.
      */
     Vst2Bridge(MainContext& main_context,
                std::string plugin_dll_path,