sequencer API users: fix get_replay_opts() leaks

sequencer API users: fix get_replay_opts() leaks

Make the replay_opts_release() function added in the preceding commit
non-static, and use it for freeing the "struct replay_opts"
constructed for "rebase" and "revert".

To safely call our new replay_opts_release() we'll need to stop
calling it in sequencer_remove_state(), and instead call it where we
allocate the "struct replay_opts" itself.

This is because in e.g. do_interactive_rebase() we construct a "struct
replay_opts" with "get_replay_opts()", and then call
"complete_action()". If we get far enough in that function without
encountering errors we'll call "pick_commits()" which (indirectly)
calls sequencer_remove_state() at the end.

But if we encounter errors anywhere along the way we'd punt out early,
and not free() the memory we allocated. Remembering whether we
previously called sequencer_remove_state() would be a hassle.

Using a FREE_AND_NULL() pattern would also work, as it would be safe
to call replay_opts_release() repeatedly. But let's fix this properly
instead, by having the owner of the data free() it.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>