[pull] main from bazel-contrib:main - #683

…3985)

Clarify the documentation for `abi_tag` in C++ Python toolchains so
that rule maintainers and users can easily map Bazel's toolchain
attributes to standard Python distribution environment variables.

Update docstrings in `python/private/py_cc_toolchain_info.bzl` and
`python/private/py_cc_toolchain_rule.bzl` to explicitly note that
`abi_tag` is the equivalent of the Python `sysconfig` variable `SOABI`,
accompanied by a reference citation to PEP 3149.

Also add `:::{versionadded} VERSION_NEXT_FEATURE` directives to all
newly
introduced toolchain fields and rule attributes.