Emergency calls support

[samcday]

Can we support dialling emergency services from 🐸 ?

[samcday]

Guido suggested in Matrix:

A "simple" test exposing a calls mock in the greeters session would show what happens (the call-ui should then be there already).

[samcday]

At the very least this depends on https://gitlab.gnome.org/World/Phosh/phosh/-/merge_requests/1517 for anything to work properly (CUI is "broken" in 0.41 libphosh builds), so I'll move this to the v0.42.0 milestone.

[samcday]

Pushing this back to 0.43

[samcday]

So actually, this already Just Works™, thanks to all the libphosh bits being in place already. I successfully dialled a test "emergency number" (my home phone number) from the phrog session on my samsung-a5.

Because gnome-calls already knows how to load emergency numbers from the SIM, the "real" emergency numbers will already show up, and should be diallable even with a locked SIM (from what I understand). Any further fixes / refinements would need to happen in libphosh / gnome-calls, or in distro packaging.

There's one essential improvement that needs to happen here, phrog needs to keep the info page selected when an emergency call is active. I've opened #100 to track that.