Notebook StdIn support to fix #5231 (#5232)

Fixes #5231 
- Add stdin handling. Has to be at UI level so add plumb through handling
- Add unit tests
- Add new StdIn component.

Testing:
Unit Tests and manual testing of following:
- Prompt for password using `getpass` in python.
   - Password prompt is hidden since "password" is true.
   - Hit enter, it completes
- prompt, stop cell running, StdIn disappears
- prompt, hit escape, stdIn disappears and stdIn request is handled.

Issues: focus isn't always set to the input even though we call focus.
Will investigate this further.

src/sql/workbench/parts/notebook/cellViews/outputArea.component.ts

@@ -22,8 +22,6 @@ export class OutputAreaComponent extends AngularDisposable implements OnInit {
 
 	private _activeCellId: string;
 
-	private readonly _minimumHeight = 30;
-
 	constructor(
 		@Inject(IWorkbenchThemeService) private themeService: IWorkbenchThemeService,
 		@Inject(forwardRef(() => ChangeDetectorRef)) private _changeRef: ChangeDetectorRef