feat: allow registering arbitrary settings for py_binary transitions (#3248)

This implements the ability for users to add additional settings that
py_binary, py_test,
and py_wheel can transition on.

There were three main use cases motivating this feature:
1. Making it easier to have multiple pypi dependency closures and shared
dependencies.
2. Making it easier to override flags for `py_wheel`.
3. Making it easier to have per-target setting of things like
bootstrap_impl, venv
   site packages, etc.

It also adds most of our config settings to the the transition
inputs/outputs for those
rules, which allows users to per-target force particular settings
without having to
use e.g. `with_cfg` to wrap a target with the desired transition
settings. It also
lets use avoid adding dozens of attributes (one per setting); today
there are
about 17 flags.

Under the hood, this works by having a bzlmod api that users can pass
labels to. These
labels are put into a generated bzl file, which the rules load and add
to their
list of transition inputs/outputs. On the target level, the
`config_settings` attribute,
which is a `dict[label, str]`, can be set to change the particular flags
of interest.

Along the way...
* Create a common_labels.bzl file for the shared label strings
* Remove the defunct py_reconfig code in sh_py_run_test.

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Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>