refactor(besadii): Extract logic for posting review comments r/2887

Currently besadii only posts comments when builds succeed, but it
might be very useful to also have a link to a build when the build is
started.

This just shuffles code around. The only functional change is that the
`labels` field in the review input is marked as `omitempty`, as this
will not be needed when posting the build start comment.

Change-Id: Id4a43fad8817c9a15da02f01ab2b781d48b46978
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3571
Tested-by: BuildkiteCI
Reviewed-by: lukegb <lukegb@tvl.fyi>

0 files changed, 0 insertions, 0 deletions