Clean up some usages of IDisposable[]

Part of #74250

- Extend `Disposable` in classes where it makes sense
- Use `DisposableStore` for lists of disposables
- Make `combinedDisposable` take arguments instead of an array (so that you can't pass in an array and then modify the array after the fact)

src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts

@@ -176,11 +176,11 @@ class MainThreadDocumentAndEditorStateComputer {
 	}
 
 	private _onDidAddEditor(e: ICodeEditor): void {
-		this._toDisposeOnEditorRemove.set(e.getId(), combinedDisposable([
+		this._toDisposeOnEditorRemove.set(e.getId(), combinedDisposable(
 			e.onDidChangeModel(() => this._updateState()),
 			e.onDidFocusEditorText(() => this._updateState()),
 			e.onDidFocusEditorWidget(() => this._updateState(e))
-		]));
+		));
 		this._updateState();
 	}