[Ray] Add Support for Disaggregating VAE and DiT

[lihuahua123]

This PR introduces support for disaggregating the VAE and DiT using Ray.
We have introduced a new argument --vae_parallel_size and --dit_parallel_size. When vae_parallel_size is set to 0, the VAE and DiT remain combined and are not separated. If vae_parallel_size is set to 1 or greater, the VAE is placed in a separate parallel Ray worker, enabling independent parallelism.

ray_world_size = vae_parallel_size + dit_parallel_size
dit_parallel_size = (data_parallel_degree *
classifier_free_guidance_degree *
sequence_parallel_degree *
pipeline_parallel_degree *
tensor_parallel_degree)

Currently, only FluxPipeline is supported for testing. Support for additional pipelines is in progress.
The separation of loading VAE and DiT is underway. For now, both modules are fully loaded within each Ray worker.
It is necessary to use the latest DistVAE.

Configuration	Average Time (seconds)
2 dit workers 0 vae worker	11.41
2 dit workers 1 vae worker	11.53
2 dit workers 2 vae workers	11.50

Each configuration was tested three times.