Backport fixes for Weston 12

Patch series to include fixes for Weston 12 (future 12.0.4 point fix release)

The following changes have been tagged since the previous bug-fix release (12.0.3):

• !1398 (merged) (Desktop-shell) fixes: middle patch dropped as that fixes an issue for a feat. that was introduced with Weston 13
• !1416 (merged) (libweston-desktop: Work around crash around opening popup menu)
• !1417 (merged) (ivi-shell: clear seat focus when surface destroyed): this required bringing in also XXX
• !1443 (merged) (backend-drm: don't force non-opaque views)
• !1445 (merged) (backend-drm: Sort planes by faked zpos)
• !1447 (merged) (desktop-shell: Fix weston crash when lost shsurf)

The first patch from !1398 (merged) had to be adapted and I had to drop the middle one (to avoid bringing the whole desktop-shell infra changes).

!1417 (merged) had a dependency on !1019 (merged) but those easy to pick without any conflicts so I took them as is.

/cc @mol !1417 (merged) technically fixes a feature added in Weston 13. Given that was easy to cherry-pick and assuming that looks with you think we can keep it. I'd like to get at least an ack wrt to them.