Clear values button error

For those willing to test, this is the patch URL:

https://git.drupalcode.org/project/config_pages/-/merge_requests/29.patch

I did a different PR, because I worked on this before finding the existing one and my approach was different.
Instead of passing the id, we can use the existing loaded config page.

I added an automated test for this functionality. In the process I found and registered 🐛 Clear values access is an invalid permission Fixed

I added the test to the existing PR. So maintainers can choose whatever approach they prefer.

Automatically closed - issue fixed for 2 weeks with no activity.