Admin: install `debug_toolbar` (#9753)
* Admin: install `debug_toolbar`
This application needs to be installed if we want to enable it later in the
`web-extra` instance. Otherwise, it fails due the static files are not in the
manifest.
By installing it by default, `collectstatic` will find this application and copy
these static files and add them in the manifest.
Note this application will only be used if `SHOW_DEBUG_TOOLBAR=True`, which is
`False` by default.
* Copy static files from `debug_toolbar` even when it's not installed
Use a "staticfiles finder" to find static files from an app that's not installed
in Django when running `collectstatic`.
This method is less intrusive and safe to run on production since it does not
execute `debug_toolbar` code on `web` instances.
* pre-commit linting
* Linting issue fixed
