rename magit-{cherry,status,wazzup}-{insert- => }-sections-hook

I intended to do this earlier but forgot to do it.  Because users might
already have customized these hooks using the old names, add aliases for
the old names, but define them as obsolete.
magit-wash-log-line: don't show "tag: " prefix as a ref

`git log --decorate' prefixes tags with "tag: ".  For a short time
we treated this prefix as a separate ref, and stop doing so now.
magit-insert-wazzup-head-line: restore old name

Give another rebase victim its old name back.
magit-insert-wazzup-branches: restore old name

Give another rebase victim its old name back.
magit-insert-wazzup-commits: use magit-format-ref-label correctly

The latter has been sanitized earlier, but
the former hasn't been adapted accordingly, until now.