PLT-4403 Add server-based channel autocomplete, search and paging (#4585)

* Add more channel paging API

* Add channel paging support to client

* Add DB channel search functions

* Add API for searching more channels

* Add more channel search functionality to client

* Add API for autocompleting channels

* Add channel autocomplete functionality to the client

* Move to be deprecated APIs to their own file

* Final clean-up

* Fixes related to feedback

* Localization changes

* Add unit as suffix to timeout constants

api/api.go

@@ -103,6 +103,7 @@ func InitApi() {
 	InitEmoji()
 	InitStatus()
 	InitWebrtc()
+	InitDeprecated()
 
 	// 404 on any api route before web.go has a chance to serve it
 	Srv.Router.Handle("/api/{anything:.*}", http.HandlerFunc(Handle404))