libarchive: Add support for translating paths during commit

libarchive: Add support for translating paths during commit

For rpm-ostree, I want to move RPM files in `/boot` to `/usr/lib/ostree-boot`.
This is currently impossible without forking the libarchive code.  Supporting
this is pretty straightforward; we already had pathname translation in
the libarchive code, we just need to expose it as an option.

On the command line side, I chose to wrap this as a regexp. That should be good
enough for a lot of use cases; sophisticated users should as always be making
use of the API. Note that this required some new `#ifdef LIBARCHIVE` bits to use
the new API. Following previous patterns here, we use the new API only if a
relevant option is enabled, ensuring unit test coverage of both paths.

For the test cases, I ended up changing the accounting to avoid having to
multiply the test count.

Closes: #1105
Approved by: jlebon