Enable status bar for notebooks (#14817)

* enable status bar for notebooks

* add onCellExecutionStart event to notebook service

* fix test, change var name

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

@@ -129,6 +129,16 @@ export interface INotebookService {
 	 * @param isTrusted True if notebook is to be set to trusted, false otherwise.
 	 */
 	setTrusted(notebookUri: URI, isTrusted: boolean): Promise<boolean>;
+
+	/**
+	 * Event that gets fired when a cell is executed.
+	 */
+	onCodeCellExecutionStart: Event<void>;
+
+	/**
+	 * Fires the onCodeCellExecutionStart event.
+	 */
+	notifyCellExecutionStarted(): void;
 }
 
 export interface INotebookProvider {