Unify token lowering in JAX to always use `stablehlo.token`.
Unify token lowering in JAX to always use `stablehlo.token`.

Right now, in JAX native execution, tokens are lowered to dummy `bool[0]`, but when exporting, we use `stablehlo.token`.

To make it work, we need to make changes across XLA/PjRt/IFRT, the main change is to allow `token` parameters in compiler and runtime.
