authz: Add DeleteAllRepoPermissionsForUser
Created by: asdine
This adds the DeleteAllRepoPermissionsForUser
to the PermsStore.
This method deletes all repository permissions for a given user and is intended to be called only when the explicit permissions API is enabled, and if so, only asynchronously.
This method will be used to remove all repository permissions without having to delete a user.
Related to #28591 (closed)