Fix the Hidden Rows problem

The source data that populates the backend DB is a cncf-internal worksheet that contains data with hidden rows.

Hidden row exclusion at maintainer-d bootstrap time though not impossible is tricky to implement. Exlcusion would mean that we would loose data about possible emeritus maintainers.

Add a feature to the web-app to "Archive" maintainers present in the DB (seeded by the internal worksheet) do not exist on Project-owned MAINTAINER/OWNERS files.

Make this a single button click on the project page, and make it apparent that it happened on case we need to restore a maintainer from that state back to "Active" or "Emeritus".

@riaankleinhans thank you for this initial feedback, looking forward to more.

This will help tidy up our records in preparation for adding maintainer line-up patches for the project.yaml files.