v21.12 service pack 2

The usual service pack discussion issue, suggestions welcome.

We can use the Sxmo backport MR for v21.12 as base: !2893

• chatty 0.6.0 upgrade (already in edge)
• possibly backport samsung-serranove modem fixes? (after went through edge, see #1274 (comment 797524967))
• backport sxmo 1.8.0 from edge: !2893
  • blog post: include sxmo upgrade notice (see #1390 (comment 826267185))
• backport !pipewire-pulse dependency added to phosh (!2890; assuming it lands in edge fast enough and has some testing there, otherwise do it in the next service pack. this prevents a bug of switching to pipewire by accident and having half-broken audio by accident when installing other packages/upgrading them)
• backport phosh 0.15.0 from edge? (has some nice visual improvements, non-numeric password support, and bug fixes, runs well for me)
  • also phoc latest release
  • small on-device installer change to allow non-numeric passwords for phosh: https://gitlab.postmarketos.org/postmarketos/pmaports/-/merge_requests/2891
• maybe pure-maps 2.9.0 to fix failing connection to osmscout-server (not sure if this actually fixes it, make sure to test this; if this is too much for SP 2, let's move to SP 3)
  • https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/30403

EDIT: targeted date: some day in CW 06 (2022-02-07 to 2022-02-13)