Port environment to nanobind

[DomFijan]

Description

Part of nanobind porting efforts.

Progress

• AngularSeparation
• BondOrder
  • Compiles
  • Tests pass
• LocalBondProjection
• LocalDescriptors
  • Compiles
  • Tests pass
• EnvironmentMatching

How Has This Been Tested?

Previous testing infrastructure is being reused.

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.

[joaander]

Thanks! There are a few TODO items that need to be addressed or removed.

[joaander]

Thanks!