Draft: intel: implement support for RPC-powered xmm7360

Continue work on !1200 in a new clean merge request.

Open review comments from the original MR:

• Move the FCC unlock parts to a separate script in data/dispatcher-fcc-unlock. Since, with RPC, there is no external library and no external CLI, we could build a simple CLI tool (i.e. a binary with its own main() in C) to run the FCC unlock procedure, then we call that tool from a script (or just make it so that the tool itself expects the same arguments as we use in the FCC unlock scripts). If the code finds that the modem is FCC locked during initialization, it will fail with an error of type MM_CORE_ERROR_RETRY and the logic in mm-iface-modem.c will run the unlock script before retrying (see https://gitlab.freedesktop.org/tuxor1337/ModemManager/-/blob/main/src/mm-iface-modem.c?ref_type=heads#L4393).
• Don't let mm_port_serial_xmmrpc_xmm7360_command (and xmm7360_command_to_byte_array) take ownership of the GByteArray body (and be responsible for freeing it), but make sure that the callers that pass that argument, also free it, e.g. using g_autoptr().

@aleksm Please lock comments in this MR and add me as a developer so that we can discuss the changes being introduced by the MR.