python: upstream rules_python PR for py_extension linking two CPython import libraries on Windows #9317

Part of #7119.

Where

• Upstream bazel-contrib/rules_python python/private/cc/py_extension_rule.bzl (_py_extension_libs_impl) and python/private/cc/py_extension_macro.bzl (win_libs_name, $(locations ...) in user_link_flags). Unfixed on main and 2.5.0-rc0.
• Our patch: patches/rules_python/single_import_lib.patch.

Fix

1. After the upstream issue from python: build and import the native extension fixture with clang-cl on Windows arm64 #7119 exists, open a small PR to rules_python with the same change as our patch: py_extension_libs takes py_limited_api and returns one import library (python3.lib/python3t.lib for limited API, else the versioned one).
2. Regression test: an analysis test under tests/cc/py_extension/ that builds the _<name>_win_libs target for a windows platform with a fake py_cc_toolchain whose libs has both python3.lib and python3XY.lib, and asserts one file for each py_limited_api value. Reuse tests/support/cc_toolchains.
3. Follow rules_python CONTRIBUTING (conventional commit title, CHANGELOG entry). No Claude trailers upstream.
4. Link the PR in python: build and import the native extension fixture with clang-cl on Windows arm64 #7119 and in the rules_python row of patches/README.md. Delete the patch, its cli/adopt/src/overrides.rs row and the README row once a release carries the fix.