Fix #4452 Notebook is reloaded with wrong kernel (#4480)

* Fix #4452 Notebook is reloaded with wrong kernel
- Await all extension registration before getting providers and providerId
To do this, we need to await way up in the NotebookInput, and promise the model that we'll have values eventually

src/sql/workbench/services/notebook/common/notebookService.ts

@@ -85,11 +85,14 @@ export interface INotebookManager {
 	readonly serverManager: azdata.nb.ServerManager;
 }
 
+export interface IProviderInfo {
+	providerId: string;
+	providers: string[];
+}
 export interface INotebookParams extends IBootstrapParams {
 	notebookUri: URI;
 	input: NotebookInput;
-	providerId: string;
-	providers: string[];
+	providerInfo: Promise<IProviderInfo>;
 	isTrusted: boolean;
 	profile?: IConnectionProfile;
 	modelFactory?: ModelFactory;