monitor: Move remaining HMP commands from misc.c to hmp-cmds.c

This requires giving them external linkage.  Rename do_help_cmd() to
hmp_help(), and do_print() to hmp_print().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230124121946.1139465-30-armbru@redhat.com>