Merge branch 'jt/diff-blobs-rpc' into 'master'

diff: Introduce `DiffBlobs` RPC

See merge request https://gitlab.com/gitlab-org/gitaly/-/merge_requests/6808



Merged-by: Toon Claes <toon@gitlab.com>
Approved-by: Karthik Nayak <knayak@gitlab.com>
Approved-by: Toon Claes <toon@gitlab.com>
Reviewed-by: Justin Tobler <jtobler@gitlab.com>
Reviewed-by: Karthik Nayak <knayak@gitlab.com>
Co-authored-by: Justin Tobler <jtobler@gitlab.com>