Refactor Noise3D palettes to optionally use dot product slants

[Astrashh]

Pull Request

Brief description.

Adds the slant.calculation-method pack manifest key, which allows switching between either the Derivative or DotProduct method of calculating slants. This PR adds the functionality of #358 to version 6.2, while maintaining parity with existing packs by setting the default method to Derivative (the current method of calculating slant).

In addition, this also provides various code refactors for palette handling in the Noise3D generator.

What Issues Does This Fix?

Implements #358 in a backwards compatible way.

Licensing

• [x] I am the original author of this code, and I am willing to release it under GPLv3.
• [ ] I am not the original author of this code, but it is in public domain or released under GPLv3 or a compatible license.

Affects of the PR

This PR should maintain parity with existing packs.

Types of changes

• [ ] Bug Fix
• [ ] Build system
• [ ] Documentation
• [x] New Feature
• [ ] Performance
• [x] Refactoring
• [ ] Repository
• [ ] Revert
• [ ] Style
• [ ] Tests
• [ ] Translation

Compatiblity

• [ ] Breaking change
• [x] Non-Breaking change.

Contribution Guidelines.

• [x] I have read the CONTRIBUTING.md document in the root of the git repository.
• [ ] My code follows the code style for this project.

Documentation

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

Testing

• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[solonovamax]

I haven't been following development, but isn't PalletInfo -> BiomePalletInfo a breaking change, which violates semver?

[Astrashh]

These changes would probably be better considered implementation details contained within the noise3d addon, rather than part of a public facing API as presented by the addon.

Perhaps we would need to formalize what addon semvers pertain to, and be more particular about visibility - as a lot of internal changes in addons could technically be considered violations if we're considering all public classes as part of an addon's public facing API.