Reporting: email and recipient discovery

[bhcopeland]

Generate a bisection report and work out who to send it to.

Report should include: what regressed, bisection log, suspect commit,
whether the revert verified it.

Recipients: get_maintainers.pl, commit trailers (Signed-off-by etc.),
Lore mbox lookup for the original patch thread.

Start with a fixed moderation list before letting it send to the wild.

There's existing code in kernelci-core/kernelci/bisect.py that does
some of this (get_recipients, get_mbox).