Move EventSource to SharedWorker (#12095)

Move EventSource to use a SharedWorker. This prevents issues with HTTP/1.1
open browser connections from preventing gitea from opening multiple tabs.

Also allow setting EVENT_SOURCE_UPDATE_TIME to disable EventSource updating

Fix #11978

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

modules/eventsource/manager_run.go

@@ -17,6 +17,9 @@ import (
 
 // Init starts this eventsource
 func (m *Manager) Init() {
+	if setting.UI.Notification.EventSourceUpdateTime <= 0 {
+		return
+	}
 	go graceful.GetManager().RunWithShutdownContext(m.Run)
 }