Add modes for `config.jax_dump_ir_to` via comma-delimited `config.jax_dump_ir_modes`.
- If `jax_dump_ir_to` is specified, dump mlir by default.
- Also gives options to dump JAXPR via `jax_dump_ir_modes=jaxpr` and an equation count profile for pprof via `jax_dump_ir_modes=eqn_count_pprof`.
PiperOrigin-RevId: 776136562