biultin/rev-parse: fix memory leaks in `--parseopt` mode

biultin/rev-parse: fix memory leaks in `--parseopt` mode

We have a bunch of memory leaks in git-rev-parse(1)'s `--parseopt` mode.
Refactor the code to use `struct strvec`s to make it easier for us to
track the lifecycle of those leaking variables and then free them.

While at it, remove the unneeded static lifetime for some of the
variables.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>