Autogeneration of Bundles for bundle uri

Bundle URIs are a useful optimization feature that allows Gitaly to advertise a pre-signed URL to a bundle. However, the creation of bundles currently must be done manually. This ends up being a maintenance burden on the admin, which we aim to remove by building in heuristics to automatically create bundles.

This series adds functionality to clones over http to automatically generate a bundle for a repository for which no bundles exist when it detects if concurrent http git clones are above a certain threshold. This is a naive first iteration to automate the generation of bundles.

Future iterations will aim to improve this, by looking at the last accessed time if a bundle does exist so we can generate a new one if bundle on object storage is old.

fixes: gitlab#462180 (closed)

This reintroduces the changes in !7037 (merged), which got reverted due to feedback.