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

webapp/platform/types/src/config.ts

@@ -196,6 +196,7 @@ export type ClientConfig = {
     PostPriority: string;
     ReduceOnBoardingTaskList: string;
     PostAcknowledgements: string;
+    DelayChannelAutocomplete: 'true' | 'false';
 };
 
 export type License = {
@@ -730,6 +731,7 @@ export type ExperimentalSettings = {
     EnableAppBar: boolean;
     PatchPluginsReactDOM: boolean;
     DisableRefetchingOnBrowserFocus: boolean;
+    DelayChannelAutocomplete: boolean;
 };
 
 export type AnalyticsSettings = {