Switched from __dataclass_transform__() to typing.dataclass_transform()

[superbobry]

Summary

This PR replaces the non-standard __dataclass_transform__() in type stubs with typing.dataclass_transform(), introduced in PEP-681.

The only difference between the two decorators is the naming of one parameter: field_descriptors= in __dataclass_transform__() is now field_specifiers=.

Pull Request Check List

• Added tests for changed code.
  Our CI fails if coverage is not 100%.
• New features have been added to our Hypothesis testing strategy.
• Changes or additions to public APIs are reflected in our type stubs (files ending in .pyi).
  • ...and used in the stub test file tests/typing_example.py.
  • If they've been added to attr/__init__.pyi, they've also been re-imported in attrs/__init__.pyi.
• Updated documentation for changed code.
  • New functions/classes have to be added to docs/api.rst by hand.
  • Changes to the signature of @attr.s() have to be added by hand too.
  • Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.
    The next version is the second number in the current release + 1.
    The first number represents the current year.
    So if the current version on PyPI is 22.2.0, the next version is gonna be 22.3.0.
    If the next version is the first in the new year, it'll be 23.1.0.
• Documentation in .rst files is written using semantic newlines.
• Changes (and possible deprecations) have news fragments in changelog.d.
• Consider granting push permissions to the PR branch, so maintainers can fix minor issues themselves without pestering you.

[hynek]

I'll leave the review to our resident typing czar but please add a news fragment.

[hynek]

Tiiin, it's greeeeeen!

[Tinche]

I'll install this branch into a bunch of our codebases and see if it's gucci.

[Tinche]

Seems to work!