fix(pypi): fix the whl selection algorithm after #2069 (#2078)

It seems that a few things broke in recent commits:
- We are not using the `MODULE.bazel.lock` file and it seems that it is
easy to
  miss when the components in the PyPI extension stop integrating well
together. This happened during the switch to `{abi}_{os}_{plat}` target
  platform passing within the code.
- The logger code stopped working in the extension after the recent
additions
  to add the `rule_name`.
- `repo_utils.getenv` was always getting `PATH` env var on bazel `6.x`.

This PR fixes both cases and updates docs to serve as a better reminder.
By
fixing the `select_whls` code and we can just rely on target platform
triples
(ABI, OS, CPU). This gets one step closer to maybe supporting optional
`python_version` which would address #1708. Whilst at it we are also
adding
different status messages for building the wheel from `sdist` vs just
extracting or downloading the wheel.

Tests:
- Added more unit tests and brought them in line with the rest of the
code.
- Checked manually for differences between the `MODULE.bazel.lock` files
in our
`rules_python` extension before #2069 and after this PR and there are no
  differences except in the `experimental_target_platforms` attribute in
`whl_library`. Before this PR you would see that we do not select any
wheels
  for e.g. `MarkupSafe` and we are always building from `sdist`.

Work towards #260.
diff --git a/python/private/pypi/extension.bzl b/python/private/pypi/extension.bzl
index 95526e4..82e580d 100644
--- a/python/private/pypi/extension.bzl
+++ b/python/private/pypi/extension.bzl
@@ -99,7 +99,7 @@
         )
 
 def _create_whl_repos(module_ctx, pip_attr, whl_map, whl_overrides, group_map, simpleapi_cache, exposed_packages):
-    logger = repo_utils.logger(module_ctx)
+    logger = repo_utils.logger(module_ctx, "pypi:create_whl_repos")
     python_interpreter_target = pip_attr.python_interpreter_target
     is_hub_reproducible = True
 
@@ -195,7 +195,6 @@
             logger = logger,
         ),
         get_index_urls = get_index_urls,
-        python_version = major_minor,
         logger = logger,
     )