[Qgis-psc] CI port to 22.04 - complete!

[Nyall Dawson]

Hi PSC,

Just reporting back that I've finished porting the CI setup to 22.04
(for master at least, the backports are still being worked through the
queue).

In the end this work involved both a lot of fixes to individual tests
to reflect changed behaviour in newer GEOS/GDAL/Qt versions, plus a
fair amount of actual bugs fixed in QGIS which were only revealed on
the newer libraries.

Here's a quick (non-exhaustive) summary of the actual fixes made
during this work:

- Fixed a crash in the rule based renderer (this one has been plaguing
us for a looong time -- it had previously been written off as an issue
in the python tests only, but during this work the Qt 6 based tests
started failing and led to the actual underlying cause of the crash!)
- Fixed an issue in the hub lines processing tool which caused failure
to save features when running on newer GDAL versions (caused by newer
GDAL rejecting geometries with nan z/m values)
- Fix virtual layer provider failing to determine correct field types
on some sqlite versions
- Fix spatialite provider incorrectly retrieving features with null
geometries when we explicitly ask for features within a given extent
on newer spatialite versions
- Fix 3d layout map exports are completely blank, and setting the 3d
layout map to copy settings from a scene completely fails
- Fix GDAL vrt items inside zip files don't show in browser
- Fix default qml style for raster layers inside zip archives isn't applied
- Fix loading gdal rasters inside zip archives which also contain a
.aux.xml file fails if only the zip archive is added as a layer

I also took the opportunity to do a bunch of cleanups to tests, and
specifically the way rendering tests were previously relying on the
orfeo toolbox cdash server to allow retrieval and comparison of
rendered vs expected images. Now it's done via a more modern approach,
making the rendered image report directly available as an artifact on
the pull request. (There's lots more we could do to make this further
developer-friendly). This removes our reliance on the orfeo toolbox
cdash server which has been broken for a number of months now.

Thanks again for the opportunity to do this work!

Nyall