MM-52173 Add setting to delay channel autocomplete (#22952)

* Add unit tests for ChannelMentionProvider.handleCompleteWord

* Add a minimum length before the ChannelMentionProvider triggers

* MM-52173 Move delayed autcomplete behind a setting

* Fix e2e test type check

* Update Textbox tests

* Add new setting to server telemetry

server/platform/services/telemetry/telemetry.go

@@ -760,6 +760,7 @@ func (ts *TelemetryService) trackConfig() {
 		"enable_app_bar":                      *cfg.ExperimentalSettings.EnableAppBar,
 		"patch_plugins_react_dom":             *cfg.ExperimentalSettings.PatchPluginsReactDOM,
 		"disable_refetching_on_browser_focus": *cfg.ExperimentalSettings.DisableRefetchingOnBrowserFocus,
+		"delay_channel_autocomplete":          *cfg.ExperimentalSettings.DelayChannelAutocomplete,
 	})
 
 	ts.SendTelemetry(TrackConfigAnalytics, map[string]any{