Cleanup test PTE structure and remove variant from shared header

[Yurlungur]

PR Summary

What it says on the can. In a previous MR (where I was cleaning things up) I broke the test in test_get_sg_eos. I'm not sure why the CI didn't catch this---going to leave that mystery to @rbberger . To reproduce, build with at least

cmake -DSINGULARITY_USE_KOKKOS=ON -DSINGULARITY_BUILD_TESTS=ON -DSINGULARITY_USE_FORTRAN=ON -DSINGULARITY_FORCE_SUBMODULE_MODE=ON ..

This MR resolves the issue and also cleans up the organization of the tests a bit by:

• Renaming the offending header file something more descriptive
• Moving the variant declarations (when they are needed by tests) into the implementation files
• Making the tests not depend on include order by more properly templating the set_eos function

I also thread through a missing cmake definition for fast logs. Unrelated to the rest of this MR.

PR Checklist

• Adds a test for any bugs fixed. Adds tests for new features.
• Format your changes by using the make format command after configuring with cmake.
• Document any new features, update documentation for changes made.
• Make sure the copyright notice on any files you modified is up to date.
• After creating a pull request, note it in the CHANGELOG.md file.
• LANL employees: make sure tests pass both on the github CI and on the Darwin CI

If preparing for a new release, in addition please check the following:

• Update the version in cmake.
• Move the changes in the CHANGELOG.md file under a new header for the new release, and reset the categories.
• Ensure that any when='@main' dependencies are updated to the release version in the package.py

[Yurlungur]

I think on github builds this was missed due to not building with kokkos. Added a build matrix that builds against kokkos to make sure we catch it.