Background

Recent pull requests #7227 #7225 and #7224 moved as much of the CI build logic from GitHub Actions to Docker containers running shell scripts. However, due to some unfortunate timing (!) these were passing when the pull requests were opened but failed when merged. This was due to ubuntugis/ubuntugis-unstable updating the GDAL package for ubuntu:20.04 (see #7228) from GDAL 3.4.3 to GDAL 3.9.3. The GDAL updates cause many differences in msautotest outputs.

In hindsight, I should have just fixed these outputs, but as at some point we'd have to move to a new version of Ubuntu I thought it would be a good time to update the Ubuntu base images and GDAL fixes..

After checking the history of the CI the last time this was done was in "Vagrant and Travis-CI: update to Ubuntu Bionic" #6111 in 2020 by @rouault, and involved 313 file changes (see also rouault@c71a4f3 updating tests from 6.4 to 7.0 where 1,571 files were changed).

Updates

I tried to keep a clean commit history with relevant comments, but due to lots of trial and error this isn't always the case.

Key updates are:

• Updated Bison 3.0.4 to Bison 3.8.2 and regenerating the parser files
• Moved all CI workflows to Docker, including the PHP MapScript builds
• Updated PostgreSQL version
• Simplified the MapScript CI builds so they don't share the full build.sh script
• Updated various expected msautotest outputs due to changes in GDAL

Notes

• Is FindGDAL still required? It looks like this is now a part of CMake: https://cmake.org/cmake/help/latest/module/FindGDAL.html
• Is vagrant still needed if we can use Docker to build MapServer and run msautotest, and the results stay consistent with the CI? Vagrant will be handled in a separate pull request.
• I have a new Python script for checking perceptual differences in image files and PDFs which helped greatly for finding image outputs that remained visually the same. I will add this to /scripts in a separate pull request.

TODOs

• the majority of failing tests are SVG outputs which do look different (sizes, background colours). For background Ubuntu 20.04 LTS (Focal Fossa, used by the CI up to now) shipped with librsvg 2.48, the new Ubuntu image uses 2.58. @mapcentia - maybe you have more knowledge about the SVG changes, and there could be a link to Fix SVG symbol sizing when width and height are with physical units  #7054?
• Fix the remaining msautotests
• Fix the cppchecks. This was updated from 1.90 to 2.7 when moving to the new Ubuntu image. The log can be found in the GitHub Actions log.