feat(config): pass kwargs to custom resolvers registered with OmegaConfigLoader - #5813

Description

Fixes #2925. Since #2896, custom resolvers can be registered with OmegaConfigLoader through CONFIG_LOADER_ARGS["custom_resolvers"], but there is no way to pass keyword arguments (such as use_cache or replace) on to OmegaConf.register_new_resolver(), which is what the issue asks for.

This implements the tuple form proposed in the issue discussion: a resolver given as a (callable, kwargs) tuple passes kwargs on to OmegaConf.register_new_resolver(); a plain callable registers exactly as before, so existing settings.py files are unaffected.

CONFIG_LOADER_ARGS = {
    "custom_resolvers": {
        "add": lambda *my_list: sum(my_list),
        "today": (date_today, {"use_cache": True}),
    }
}

Development notes

• _register_new_resolvers() unpacks the tuple and forwards the kwargs; the type hints and the OmegaConfigLoader docstring are updated to match.
• Docs: docs/configure/how_to_use_templating.md shows the tuple form.
• Tests: test_custom_resolvers_with_kwargs registers a counter resolver twice (cached via the tuple form and uncached as a plain callable) and asserts the cached interpolations resolve equal while the uncached ones do not. On current main the test errors at registration (TypeError: resolver must be callable).
• tests/config/ suite: 94 passed. ruff format clean. ruff check reports only the same 4 pre-existing findings as on main. The full repo suite and mypy --strict were not run; happy to address anything CI turns up.

Developer Certificate of Origin

All commits are signed off.

Checklist

• Read the contributing guidelines
• Linked to a relevant GitHub issue
• Signed off each commit with a DCO
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes