CI: various improvements

Add testlog.txt as build artifacts: If unit tests fail, add the testlog.txt of the failed run to the pipeline's artifact. We can inspect it and find the cause easier.

Fix pipelines using different Alpine versions: Using Alpine versions other than latest was not supported by ci-templates. Now they are supported so let's use the latest revision of ci-templates.

Use Fedora 40 for Tier 1, as F41 is still a bit unstable. Also allow to specify manually what Fedora version to use for Tier 1 in distros-info.yml, so it is automatically generated by distros_support.py.