Bump setuptools to 71.0.*

[Avasam]

Closes #12359

Of note:

• setuptools now incidentally ships its tests (Install all the files pypa/setuptools#4479 reverted pypa/setuptools@fbc9bd6 )
• Simplify vendoring and declare dependencies optionally pypa/setuptools#4457
  • pkg_resources no longer has a _vendor folder, it's now combined under setuptools/_vendor
  • setuptools.extern and pkg_resources.extern don't exist anymore
  • installed dependencies are preferred over vendored ones, meaning we can accurately use real stub dependencies (removes _vendored_packaging) (decided to defer to later, see comment below)
  • dependencies are listed under the [core] extra, which means stub_uploader can statically pick them up
• Distribution.patch_missing_pkg_info was removed Remove _patched_dist pypa/setuptools#4493
• mypy 1.11 update allows removing the temporary _LoaderProtocol class

[Avasam]

Removing _vendored_packaging requires packaging to be added to stub_uploader's allowlist. Should we do that and wait, or keep _vendored_packaging for now to to get the 71.0 update out asap ?

Note that this is only needed for pkg_resources, which is likely to be removed from types-setuptools in about 6 months anyway 😉 pypa/setuptools#4409

Edit: I opted to keep _vendored_packaging for this PR

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉