Add an option to bypass review for specified contributors

We'd like to discuss a feature that allows bypass of the requirement for approvals for particular contributors (/maintainers) on specified projects - where a firm's internal contribution policies permit.

> The requirement for reviews can sometimes add friction to contribution, for project maintainers in particular where frequent smaller contributions need to be made. Such contributors would generally be senior engineers in a firm and potentially trusted to contribute and represent their firm without tight supervision - but still require auditable logs of their contributions and/or a feature to facilitate periodic review. Any such bypass would not apply to other contributors from that firm.

_Originally posted by @kriswest in [#1350](https://github.com/finos/git-proxy/issues/1350#issuecomment-3799624807)_

This may already be possible via other Git Proxy features - but it would seem sensible to allow it to be configured in the admin interface and for it to be supported cleanly the pre-processors.