[modular] Add LTX Video modular pipeline (#13378)
* Add modular pipeline support for LTX Video
* Fix guidance_scale passthrough to guider
* Add LTX modular pipeline tests
* Add LTX image-to-video modular pipeline
* Fix i2v VAE dtype mismatch
* Add cache_context to denoiser for CFG parity
* Address review feedback
* Generate auto docstrings for LTX assembled blocks
* Fix ruff lint and format issues
* use InputParam/OutputParam templates and ruff check
* address all review
* Lift LTXVaeEncoderStep out of I2V core denoise into its own auto block
* unused declarations
* Fix check_copies: sync retrieve_timesteps and drop unsupported Copied from tags
* Address review: remove unused code, add LTXAutoBlocks, refactor I2V latents flow
* removed LTXBlocks,LTXImage2VideoBlocks
* Update test to use LTXAutoBlocks
* workflow map and auto docstring
* Add LTXVideoPachifier, workflow map
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Co-authored-by: YiYi Xu <yixu310@gmail.com>
