Third-party transitive dependencies seem to be packaged into wheels incorrectly

# 🐞 bug report

### Affected Rule

py_wheel

### Is this a regression?

Doubtful

### Description

When building a wheel using `py_wheel`, third-party pip requirements are being installed into an incorrect directory, preventing them from being properly installed/used in Python environments.

## 🔬 Minimal Reproduction

```
load("@rules_python//python:defs.bzl", "py_binary", "py_library")
load("@rules_python//python:packaging.bzl", "py_package", "py_wheel")
load("@python_deps//:requirements.bzl", "requirement")

filegroup(
name = "srcs",
srcs = glob(
[
"**/*.py",
"*.py",
],
exclude = ["tests/**"],
),
)

py_deps = [
requirement("behave"),
]

py_library(
name = "regression_harness",
srcs = [":srcs"],
visibility = ["//bt:__subpackages__"],
deps = py_deps,
)

py_package(
name = "regression_harness_pkg",
deps = [
":regression_harness",
],
)

py_wheel(
name = "regression_harness_wheel",
distribution = "regression_harness",
version = "1.0.0",
deps = [
":regression_harness_pkg",
],
)
```

## 🔥 Exception or Error

The wheel builds as usual, and looks (at least mostly) correct. However, upon installing the wheel, we see the following:

gitpod /workspace/tribe $ ls /tmp/test/lib/python3.8/site-packages/

bin                       pip-24.1.2.virtualenv                  site-packages

bt                        pkg_resources                          _virtualenv.pth

_distutils_hack           __pycache__                            _virtualenv.py

distutils-precedence.pth  regression_harness-0.0.8940.dist-info  wheel

include                   setuptools                             wheel-0.43.0.dist-info

lib                       setuptools-57.4.0.dist-info            wheel-0.43.0.virtualenv

pip                       setuptools-57.4.0.virtualenv

pip-24.1.2.dist-info      share

`regression_harness` was in fact installed, and is available, but the third-party transitive dependencies are within a **nested** site-packages directory _within_ the site-packages.

gitpod /workspace/tribe $ ls /tmp/test/lib/python3.8/site-packages/site-packages/

behave                  parse-1.20.2.dist-info  parse_type-0.6.2.dist-info  six-1.16.0.dist-info

behave-1.2.6.dist-info  parse.py                __pycache__                 six.py

__init__.py             parse_type              setuptools_behave.py

Of course, this means that they're not available within the environment, as that directory is not part of the PYTHONPATH.

I have tried stripping the `site-packages` prefix when building the wheel, but this makes the wheel file invalid as it will contain multiple `.dist-info` files.

Am I doing something incorrectly? This seems like a bug to me, but I can't imagine that others wouldn't have seen this.

## 🌍 Your Environment

**Operating System:**

  

Ubuntu Focal

  

**Output of `bazel version`:**

  

gitpod /workspace/tribe $ bazel version

Bazelisk version: v1.17.0

Build label: 6.2.1

Build target: bazel-out/k8-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar

Build time: Fri Jun 2 16:59:58 2023 (1685725198)

Build timestamp: 1685725198

Build timestamp as int: 1685725198

  

**Rules_python version:**

  

0.27.1

e85ae30de33625a63eca7fc40a94fea845e641888e52f32b6beea91e8b1b2793

  

**Anything else relevant?**