FR: Status check to tell me if I'm breaking cloud.google.com about repo-automation-bots

[orthros]

This is something I've wanted for a long wile and have brought up with other team members. There are some "guidances" on writing snippets, and I think putting them out into a linter would be a good first start. In terms of "are we about to break cloud.google.com"... that might have to be a kokoro job as the infra to detect that might not be available to our production environment.

As a follow up: one of these bots could detect if a region was changed for a snippet, and comment on the PR with what the new "state" of the snippet would be based on the changes in the PR.

[tmatsuo]

This is now implemented as a warning in a issue comment on the PR.
My plan is to change it to failing status check.

[tmatsuo]

It's finally done