Notebooks: re-factor grid streaming (#12937)

* refactor grid streaming (convert to data first)

* change convertRowsToHtml method to return value

* remove griddataconversioncomplete checks

* send row data from STS to gridoutput component

* clean up code

* send data updates to cell model

* serialize cell output at the end of cell execution

* remove unused parameters

* update output contents instead of output reference

* remove unnecessary promise

* move azdata changes to proposed

* update comment

src/sql/workbench/contrib/notebook/test/stubs.ts

@@ -43,9 +43,6 @@ export class NotebookModelStub implements INotebookModel {
 	get sessionLoadFinished(): Promise<void> {
 		throw new Error('method not implemented.');
 	}
-	get gridDataConversionComplete(): Promise<any[]> {
-		throw new Error('method not implemented.');
-	}
 	get notebookManagers(): INotebookManager[] {
 		throw new Error('method not implemented.');
 	}