Align projection tensor calculations with master

[Jacob-Stevens-Haas]

This PR extracts the simplified routines for creating the projection tensors. The simplification is possible because of explicitly relying on the PolynomialLibrary through the helper function _build_lib_info, which allows methods to look up indexes for relevant terms. As a result, the PQ and PL matrices now have tests to ensure they are built correctly.

We also remove the check_P_tensors function, because we have explicit tests.

Finally, this also

• moves a few other helper functions from master into trapping_extended to further limit the merge conflicts.
• cherry-picks a commit from master to improve CI

For review, start with the tests, then the projection calculations. If desired, see the helper functions.

[Jacob-Stevens-Haas]

Ok I'm going to merge this one now, I need to start digging into the algorithm stuff