Refactor: libcib: Support transactions for CIB file clients

See the commit "Refactor: based: Support CIB transactions" for details
on how this all works. This implementation for CIB file clients is
very similar to the pacemaker-based implementation, but simpler.

An upcoming commits will implement CIB transactions in the client API.

Ref T185

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>