Workhhorse logs should report bytes read via labkit

(placeholder)

At present, workhorse only records bytes written.

Labkit access logs should also record bytes read from the client.

This would help in investigations such as https://gitlab.slack.com/archives/CD6HFD1L0/p1601310922104600 in which CI traces led to a high volume of NFS traffic.

Proposal

Adapt the approach in https://gitlab.com/gitlab-org/gitlab-workhorse/-/blob/926eb55f52774c058ec876877015977cafe3b459/internal/git/git-http.go#L44-50 to apply to all requests, and preferably package this in labkit along with the other logging code.