Roll out iwd instead of wpa_supplicant in pmOS

Follow up on pmbootstrap#1864 (closed) and postmarketos#45 (closed), to have the discussion in one place and to have a more concrete plan to roll it out. I suggest we roll it out as follows:

• adjust all kernels for devices in main and community to have iwd support enabled
• enforce it in CI (like we enforce nftables for main/community, see pmaports.git .ci/testcases/test_kernel.py)
• implement selection in postmarketos-base for iwd / wpa_supplicant using _pmb_select (pmbootstrap!2132 (merged))
  • we should note in the description, that only wpa_supplicant may work with devices in testing
• create a wiki page about iwd, that also explains how one can switch to iwd from wpa_supplicant in an existing installation, and back
• verify that iwd works well with each device in main/community, get bugs fixed if needed; let this take the time it needs
• switch to iwd by default (for the many benefits outlined in postmarketos#45 (closed)) by making it the recommended provider, so the "pmbootstrap init" selection from _pmb_select recommends it. this should lead to bpo image building also installing it

Help welcome. "adjust all devices in main and community" and "implement selection in pmos-base" could be started in parallel.