deprecate/remove bvmdebug and bvmconsole

[Rob Wing]

I've got a review in for the removal of bvmdebug and bvmconsole.

This removes the `-b` and `-g` flag from bhyve(8), these were marked as
'will be deprecated in a future version' when they were introduced.

I'm not sure if a deprecation notice is necessary/needed before removal
though.

The review can be found at: https://reviews.freebsd.org/D27490

Mentioned in PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233230

Any objections?

Thanks,
Rob