nullify actionbar and view item context on dispose, remove notebook overview ruler on dispose (microsoft#167817)

fixes microsoft#167813

Author: jrieken

src/vs/base/browser/ui/actionbar/actionViewItems.ts

@@ -253,7 +253,7 @@ export class BaseActionViewItem extends Disposable implements IActionViewItem {
 			this.element.remove();
 			this.element = undefined;
 		}
-
+		this._context = undefined;
 		super.dispose();
 	}
 }

src/vs/base/browser/ui/actionbar/actionbar.ts

@@ -579,6 +579,7 @@ export class ActionBar extends Disposable implements IActionRunner {
 	}
 
 	override dispose(): void {
+		this._context = undefined;
 		this.viewItems = dispose(this.viewItems);
 		this.getContainer().remove();
 		super.dispose();

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -2929,6 +2929,8 @@ export class NotebookEditorWidget extends Disposable implements INotebookEditorD
 		this._baseCellEditorOptions.forEach(v => v.dispose());
 		this._baseCellEditorOptions.clear();
 
+		this._notebookOverviewRulerContainer.remove();
+
 		super.dispose();
 
 		// unref