[3.4] CI: Partially sync workflows and actions with 3.x branch

[akien-mga]

• 3.4 version of [3.5] CI: Fully sync workflows and actions with 3.x branch #98937.

Differences to 3.x:

• All: Stick to ubuntu:20.04 runners for now, as porting to newer ones implies fixing a number of compilation warnings which may not be worth the trouble for an EOL branch
• All: Keep 3.4 base branch
• Build: Keep the --jobs=2 SCons argument, 3.4 and earlier don't have the auto job count detection
• Android: Keep Java 11
• Web: Keep Emscripten 2.0.25
• Linux: Don't add the minimal template build, which relies on a number of fixes and improvements not made in that branch
• Static checks:
  • Update to ubuntu:22.04 instead of ubuntu:24.04 so we can pin clang-format-13 instead of 16, keeping the same version as prior, so we don't have to do style changes to this EOL branch
  • Don't add the gitignore_check.sh static check as we didn't do the fixes it helps enforce
  • Don't add the class reference schema static check as we didn't backport that either
  • Keep previous copyright_header.py, as we didn't do the big copyright update to "present" in 3.4 and earlier
  • Keep previous clang_format.sh with needed exceptions for some .java files