Expose `sysconfig` variables in `PyRuntimeInfo` provider

# 🚀 feature request

Downstream rules are potentially interested in the selected toolchains configuration.
Specifically, building C extension modules depends on things like `EXT_SUFFIX` to create proper extensions supporting the chosen interpreter.
Because that suffix ends up in file names, downstream rules may need that value at configure time, when they can't query the interpreter.
But the `@rules_python` `repository_rule` can easily determine these variables before configure time, for each registered toolchain.

This is related to:
- https://github.com/bazelbuild/rules_python/issues/824
- https://github.com/nicholasjng/nanobind-bazel/issues/61
- I'm sure other downstream bazel tooling related to C extensions would like this as-well

### Relevant Rules

This feature would ultimately need changes to:
- `PyRuntimeInfo` (basic schema)
- `py_runtime` (so that third party toolchains/interpreters can provide that information too)
- the internal pluming providing the `@rules_python` provided internal toolchains

### Description

`PyRuntimeInfo` needs a field `ext_suffix`, or alternatively `sysconfig_variables` (for future extension).
At extension instantiation time, when setting up the toolchain repos, the respective interpreters should be queried for their `ext_suffix`; alternatively, that information could be determined offline.

Commencez par le schéma PyRuntimeInfo et la règle py_runtime mentionnée dans l’issue, puis suivez la configuration du dépôt interne de toolchain qui fournit les interpréteurs enregistrés. Consultez les issues #824 et nanobind-bazel#61 pour le contexte ; le travail est terminé lorsque les données de sysconfig telles que ext_suffix sont disponibles pour les règles en aval et peuvent être fournies par des toolchains tierces.

Rédigé par le modèle d'indexation à partir du texte de l'issue.