Close sidebar when running vscode tests (#2797)

## Checklist

- [/] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [/] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [/] I have not broken the cheatsheet

---------

Co-authored-by: Phil Cohen <[email protected]>

packages/vscode-common/src/testUtil/openNewEditor.ts

@@ -33,6 +33,9 @@ export async function openNewEditor(
     await editor.edit((editBuilder) => editBuilder.setEndOfLine(eol));
   }
 
+  // Many times running these tests opens the sidebar, which slows performance. Close it.
+  vscode.commands.executeCommand("workbench.action.closeSidebar");
+
   return editor;
 }