Favorites management - escalate roles so that user unable to manage own git favorites doesn't get stuck

Users with limited privileges can't add/edit their own favorites. The upstream issue for this (DP-435671) has been closed with no plans to fix it, so we need to work around the issue in git-source-control itself.

Proposed solution:
Use $$$AddAllRoleTemporary in a new %zpkg.isc.sc.git class to wrap calls to manage favorites.