[review] Rename Basic Connect Extensions service

[Aleksander Morgado]

Hey Dan, Ben & all,

See https://gitlab.freedesktop.org/mobile-broadband/libmbim/merge_requests/3

This MR is to clearly specify that the service is defined by
Microsoft, not a generic service, so the naming is following that of
other MS-defined services.

I'll update ModemManager accordingly (for the PCO related stuff) when
merging this MR, if you're happy with it.

-- 
Aleksander
https://aleksander.es