Add instrumentation to PTE solver and expose runtime parameters

[Yurlungur]

PR Summary

In riot we are looking into some load balancing questions and performance of the PTE solver. To support this, I make the following changes to the PTE solver:

• I expose the mix_params namespace as a container struct that can be set at runtime
• I modify the return value of the PTESolver function to include some instrumentation, such as the number of iterations the solver took.
• I expose a verbosity parameter to suppress warnings if we want.
• I clean up the documentation and variable names a bit.

I also split up the modifier tests to help with compile times and do a small bug fix which was causing problems with the newest version of gcc.

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

[jhp-lanl]

Looks good to me. The majority of the DIFFs are just size_t vs int or adding params. it seems. I've commented on anything else that I didn't understand.

Thanks a bunch for these fixes! They are most welcome!