This is a flag to start leveraging of the new code paths. The Starlark
implementation has been added in 1.4 and has been reverted in the latest
release candidates. The `env` variable will be a good way to roll it out
more
gradually and get more testing.

For now we are switching only the `whl_library` internals as the
`requirements.txt` files from `uv` may use `*` in `python_full_version`
and
`platform_version` that are not yet fully supported (bazel-contrib#2826).

Main goals for this is to start using Starlark implementation so that we
don't
have any hidden variables. What is more, having this in Starlark is the
most
maintainable long-term solution for supporting cross-platform builds.

Work towards bazel-contrib#260

---------

Co-authored-by: Richard Levasseur <richardlev@gmail.com>

Fixes:
```
ERROR: /Users/fmeum/git/rules_python/tests/pypi/env_marker_setting/BUILD.bazel:3:30: Illegal ambiguous match on configurable attribute "platform_machine" in //tests/pypi/env_marker_setting:test_expr_python_full_version_lt_negative_subject:
@@platforms//cpu:aarch64
@@platforms//cpu:arm64
Multiple matches are not allowed unless one is unambiguously more specialized or they resolve to the same value. See https://bazel.build/reference/be/functions#select.
```

Work towards bazel-contrib#2850.
Work towards bazel-contrib#2826.

…rib#2856)

This reuses the previous work by @vonschultz who implemented
a PEP440 version normalizer. We extend it and use it in the
PEP508 marker evaluation.

Summary:
- Extend the normalization parser to output individual parts
  of the versions to the parsing context.
- Re-implement all of the version comparison calls to use the
  parsed version.
- Add extra validation for `.*` usage in the environment markers
- Fallback to non-version matching in the environment markers
  if one of the sides is not a version.
- Rename the original normalizer file to `version.bzl` because
  as far as Python is concerned this is the only version that
  there can be. We could in theory probably reuse this in other
  code where we are parsing the Python interpreter version many
  times, but this is left for the future.

Fixes bazel-contrib#2826
Work towards bazel-contrib#2821

---------

Co-authored-by: Richard Levasseur <richardlev@gmail.com>
Co-authored-by: Richard Levasseur <rlevasseur@google.com>