repository: Remove housekeeping from Cleanup RPC

This MR removes the call to housekeeping from the Cleanup() RPC. This request is run synchronously when a push is received, creating the risk that a failure here will block users from pushing their changes.

We have found that the stale files and refs checks run as part of housekeeping may exceed 60 seconds for larger repositories that are hosted on NFS or poorly packed, causing pushes to consistently timeout for some self-managed customers.

Also, move the housekeeping call in GarbageCollect to run prior to git gc being invoked. This should prevent some GC failures by removing stale lockfiles. I don't think this will increase the risk of stale objects/pack/tmp_* files sticking around from a killed/failed git gc as the RPC would error out prior to housekeeping in that scenario.

Closes #3581 (closed)