Investigate how to add default checks to repositories for when API is down

As raised in eclipsefdn/helpdesk#5921 (comment 3718564), when there is a full service outage where the Git ECA service is fully unavailable, the ECA validation statuses are not set in pull requests. As the 2 first steps in receiving a merge request event, we save a record that the check was requested and set the initial status. When the service is fully down, these checks are not created.

There is a mechanism in GitHub called "Required Checks" that allow some status checks to be defined as set by default, as seen in https://github.com/adoptium/TKG/pull/697 which was created during the recent full outage. We should investigate how we could potentially extend this functionality, or otherwise apply these checks from within GitHub to reduce any gaps that could be experienced during outages.