The goal of this change is to catch PRs that introduce new warnings sooner.
To help pass the environment variable more easily, rename the jax_test Bazel test macro to jax_multiplatform_test, and introduce a new jax_py_test macro that wraps py_test. Add code to both to set the environment variable.
Add code to suppress some new warnings uncovered in CI.
PiperOrigin-RevId: 678352286
The motivation here is to gradually replace all dynamic lookups on `jax.config`
with statically-typed state objects, which are more type checker/IDE friendly.
This is a follow up to #18008.