Ci Update runners and fix tests

[jarzec]

In .github/workflows/:

• rename regression-tests.yml → regression-tests.yaml for consistency,
• improve the workflows in general,
• remove the deprecated runner images (macos-13) and their respective test data,
• comment out tests on Windows util builds on Windows runners are fixed (this makes the tests all-green).

Adjust regression-tests/run-tests.sh accordingly.
In addition the -include-std cppfront option was added for pure2-* tests. This is necessary after the updates of test files from #1405 (thanks @gregmarr).

[jarzec]

@hsutter I did this to allow the tests to turn all green without the failure caused by build failures on Windows runners.
This will allow to quickly see if a PR adds regression or not without going into details of the failure each time and see if it only the Windows runner that fails.

I will try to have a look at those failures and fix the root cause. When it is fixed I will reenable Windows runners.

The same applies to the regression test workflow.

[hsutter]

Thanks again for this!