Notebook toolbar UI improvement (#5282)

Fixed  #5236
- Change the icon to blue image. Existing icons are not deleted. We will use them when the icons are - - moved as the secondary actions.
- Change the font size to 13px
- Change the height to 21px
- Move Add actions to the left

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

@@ -383,10 +383,10 @@ export class NotebookComponent extends AngularDisposable implements OnInit, OnDe
 		this._actionBar = new Taskbar(taskbar, { actionItemProvider: action => this.actionItemProvider(action as Action) });
 		this._actionBar.context = this;
 		this._actionBar.setContent([
-			{ element: kernelContainer },
-			{ element: attachToContainer },
 			{ action: addCodeCellButton },
 			{ action: addTextCellButton },
+			{ element: kernelContainer },
+			{ element: attachToContainer },
 			{ action: this._trustedAction },
 			{ action: this._runAllCellsAction },
 			{ action: clearResultsButton }