Convert PMFT to use nanobind

[tommy-waltmann]

Description

This PR converts the PMFT module to use nanobind.

Motivation and Context

This PR is part of a series of PRs which removes the cython from freud.

How Has This Been Tested?

If existing tests pass, this PR should be good to go.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds or improves functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation improvement (updates to user guides, docstrings, or developer docs)

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• I have updated the documentation (if relevant).
• I have added tests that cover my changes (if relevant).
• All new and existing tests passed.
• I have updated the credits.
• I have updated the Changelog.