Merge branch 'ps/connected-generic-promisor-checks'

The connectivity check has been refactored to search for promisor objects in a generic way using the object database interface, rather than iterating packfiles directly. This allows connectivity checks to work properly in repositories that do not use packfiles. * ps/connected-generic-promisor-checks: connected: search promisor objects generically connected: split out promisor-based connectivity check odb/source-packed: support flags when iterating an object prefix odb/source-packed: extract logic to skip certain packs