Kusto - ADS Core changes (#11750)

* ADS Core changes

* Generic fix to get language mode based on providerId

* Addressed comments

* Fix failing tests

* Fix for "New Notebook" from file menu option

* Remove line

* Fix for merge conflict

* Add removed comment back

* Addressed comments

Co-authored-by: Monica Gupta <mogupt@microsoft.com>

src/sql/platform/connection/test/common/testConnectionManagementService.ts

@@ -287,6 +287,10 @@ export class TestConnectionManagementService implements IConnectionManagementSer
 		return undefined!;
 	}
 
+	getProviderLanguageMode(providerName?: string): string {
+		return undefined!;
+	}
+
 	getConnectionIconId(connectionId: string): string {
 		return undefined!;
 	}