This new interface allows modems to expose the list of available
connection profiles stored in the device and edit or delete them; as
long as the underlying device/protocol allows it.
Include the new SAR interface in the build so that gdbus-codegen
generates support for it in libmm-glib as well as proper documentation
in the API reference.
It's pointless to have libmm-common around, just merge it into libmm-glib and
make ModemManager depend on libmm-glib directly. At the end, the non-common
stuff in libmm-glib is really minimal.