Accomodate P-T preferred inputs in PTE solvers

[jhp-lanl]

PR Summary

This PR changes the PTE solver base class to accomodate EOS models whose preferred inputs include pressure. In this case, a lookup won't be performed to get the initial pressure for the PTE solver and instead the provided pressure for this material will be used.

Fixes #581

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]

One minor comment, which I think should be addressed before merge (and tests should pass) but I'm approving now.

[jhp-lanl]

Let's make sure the LANL tests pass before we merge this

[Yurlungur]

Let's make sure the LANL tests pass before we merge this

👍 yep definitely

[jhp-lanl]

Tests pass