Improve detection when LS is fully loaded for IntelliCode (#12853)

* Fix path

* Actually fix settings

* Add news

* Add test

* Format

* Suppress 'jediEnabled' removal

* Drop survey first launch threshold

* Wait for client ready

* Handle async dispose

Author: Mikhail Arkhipov

src/client/activation/languageServer/languageServerProxy.ts

@@ -102,9 +102,13 @@ export class DotNetLanguageServerProxy implements ILanguageServerProxy {
     }
     @captureTelemetry(EventName.PYTHON_LANGUAGE_SERVER_READY, undefined, true)
     protected async serverReady(): Promise<void> {
-        while (this.languageClient && !this.languageClient!.initializeResult) {
+        // languageClient can be disposed in awaits.
+        while (this.languageClient && !this.languageClient.initializeResult) {
             await sleep(100);
         }
+        if (this.languageClient) {
+            await this.languageClient.onReady();
+        }
         this.startupCompleted.resolve();
     }
     @swallowExceptions('Activating Unit Tests Manager for Language Server')

src/client/activation/node/languageServerProxy.ts

@@ -146,9 +146,12 @@ export class NodeLanguageServerProxy implements ILanguageServerProxy {
         NodeLanguageServerProxy.versionTelemetryProps
     )
     protected async serverReady(): Promise<void> {
-        while (this.languageClient && !this.languageClient!.initializeResult) {
+        while (this.languageClient && !this.languageClient.initializeResult) {
             await sleep(100);
         }
+        if (this.languageClient) {
+            await this.languageClient.onReady();
+        }
         this.startupCompleted.resolve();
     }