feat(ui): implement new event stream connection logic

Added a new event stream connection method to enhance the handling of
server events. This includes a reconnect mechanism for improved reliability
in case of connection errors. The configuration now allows toggling the
new event stream feature via `devNewEventStream`. Additionally, tests
were added to ensure the new functionality works as expected, including
reconnection behavior after an error.

Signed-off-by: Deluan <deluan@navidrome.org>

ui/src/config.js

@@ -32,6 +32,7 @@ const defaultConfig = {
   enableNowPlaying: true,
   devShowArtistPage: true,
   devUIShowConfig: true,
+  devNewEventStream: false,
   enableReplayGain: true,
   defaultDownsamplingFormat: 'opus',
   publicBaseUrl: '/share',