Use Workhorse SendArchive when serving a Go module that has no exclusions

Summary

The Go proxy MVC implemented in !27746 (merged) builds archives directly because the Go proxy protocol has requirements that cannot be satisfied with Workhorse:SendArchive. Specifically, subdirectories containing go.mod must be excluded. git archive (thus Gitaly:RepositoryService.GetArchive thus Workhorse:SendArchive) does not support exclusions, so archives must be constructed via another method.

However, if a Go module does not have any such exclusions, Workhorse:SendArchive can and should be used.

This relates to #218083

Improvements

In the majority of cases, Go proxy archive generation would be handled via an existing mechanism, Workhorse:SendArchive. This would improve the performance characteristics of the Go proxy and is a step towards removing the feature flag.

Risks

This will require minor changes to send_git_archive.

Involved components

• [Rails] Gitlab::Workhorse#send_git_archive needs support for specifying the archive entry prefix.