Convert VCR comment formatting to use a go template

[melinath]

What kind of contribution is this issue about?

Pull request UX

Details

Currently we format the VCR-related comments posted to PRs by manually building strings bit by bit. This is difficult to reason about or test. We should instead build data structures and then pass them into a Go template, similar to generate_comment.

References

No response

[iyabchen]

I can take this ticket.