For many Gitaly RPCs, previously the `gitaly_duration_s` log timings
only accounted for the initial request/response time. We now measure the
total time it takes to consume the streaming response for the following
RPCs:

1. GetBlob
2. GetLFSPointers
3. GetBlobs
4. GetNewLFSPointers

This came up in https://gitlab.com/gitlab-org/gitlab/-/issues/222247.

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/30334