refactor: makes internal utilities private

[mdevolde]

refactor: makes internal utilities private

Why the pull request was made

In prevision of the breaking release, move some internal utilities to a private module, and makes other internal stuff private by renaming them.
This PR is a breaking change.
Having private stuff ensure that we can modify them as we want without having to make a breaking release.

Summary of changes

• Renaming constants/functions/classes in the project to make them private.
• Create an internal module _internals.
• Move _compat to _internals/compat
• Move some stuff from utils to _internals/utils (keep a utils module to expose some utilities like correct).
• Move api_types to _internals/api_types.
• Move safe_zip to _internals/safe_zip.
• New match.is_check_match function to be able to correctly type Match.__init__ (in casual situations, a user doesn't need to create matches by himself but because Match creation is public, tools to do it must be available).

Screenshots (if appropriate):

Not applicable.

How has this been tested?

Applied local tests.

Resources

Not applicable.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters, checked types and tests.