[jax:cpu] Add a test config to run JAX with new XLA:CPU runtime
XLA:CPU is migrating from compiling monolithic LLVM function for the whole HLO module to a thin runtime with separate functions for each kernel (fusion, individual operation, library call, etc.). While new runtime is not enabled by default we will use explicit opt-in on tests that are already compatible.
This tag will be removed after XLA:CPU will switch to the new runtime by default.
PiperOrigin-RevId: 640022517
