Support Python 3.15 free-threaded in Bazel builds

- Update the rules_python patch to support `abi3t` wheel tags and fix `cp315` platform string generation.
- Add explicit free-threaded target platforms in MODULE.bazel.
- Replace macro-time dependency exclusion in jax.bzl with `//:pypi_optional_*` aliases in BUILD.bazel that resolve to an empty library on unsupported configurations (e.g. portpicker on 3.15 free-threaded).