This adds a new Plugin.track_info_updated method, enabling the user to get the name and color of the track associated with the Plugin. These two attributes were selected as they are both present in the data provided to VST3's IInfoListener and CLAP's CLAP_EXT_TRACK_INFO.
VST3 support was tested on Ableton, Bitwig, Cubase, FL Studio, and Reaper. Of these, only FL Studio does not call setChannelContextInfos, and so the plugin gets no TrackInfo in this case.
CLAP support was tested in Bitwig. It appears that version 7.68 of Reaper was the first to support the CLAP_EXT_TRACK_INFO, but my version of Reaper predates this.
Track info display was added into the gain_egui example.