Enable flake8-type-checking

[Avasam]

Summary of changes

Enables flake8-type-checking (TC) for the followings protections without having to put too much thought into it:

• Helps prevent accidental circular imports
• Reduce runtime cost of importing typing-only symbols (more of a micro-optimization, but works towards [BUG] Importing setuptools is slow and takes nearly half a second #3441)
• Reduces details leaks into modules at runtime

Not applying to stdlib (typing-only-standard-library-import (TC003)) because:

• stdlib is not at risk of causing a circular import
• We can reasonably assume that most stdlib imports will be part of the initial import chain anyway
  • Although I could be wrong, worth checking
• stdlib imports are clearly not meant as re-exported symbols for the public API

Pull Request Checklist

• Changes have tests
• News fragment added in newsfragments/.
  (See documentation for details)