ci: Check config store docs are up-to-date

It's very easy to forget to regenerate the rst documentation for the configs after modifying a yaml. So let's check if it's up-to-date in the CI and fail if not. Simply regenerate the docs and check if there is any difference vs the repo.

Suggested-by: Sudeep Holla sudeep.holla@arm.com Signed-off-by: Ryan Roberts ryan.roberts@arm.com