Supporting `setuptools-git-version` as a version provider

[ktbarrett]

I would like to scikit-build-core and setuptools-git-version together in projects.

setuptools-git-version is similar to setuptools-scm, but is less opinionated and more configurable, only concerns itself with including the git version, and better supports shallow clones.

I see there is support in this repo for setuptools-scm, but comments mention that ideally it should not live in this repo. So for supporting setuptools-git-version, I will add support in setuptools-git-version. So this is more of a question of "what is the API of a version provider that scikit-build-core requires?"

I see:

def dynamic_metadata(
    field: str,
    settings: dict[str, object] | None = None,
) -> str:
    ...


def get_requires_for_dynamic_metadata(
    _settings: dict[str, object] | None = None,
) -> list[str]:
    ...

The first function takes a field from the list of dynamic fields from pyproject.toml and a settings object. What is passed to the settings arguments? I doubt I'll use it, but I'm curious. And the second one is dependencies for this plugin's function with that same settings object.