Cosmos3 ModularPipeline (#14110)
* Cosmos3 ModularPipeline initial commit
* Fix from_pretrained for modular pipleine without modular_model_index.json
* Isolate text prep inside Cosmos3TextEncoderStep; add Cosmos3ActionTextStep
* Cosmos3 modular encode/decode flow
* Drop device/dtype required InputParams; use components._execution_device and model dtype
* Add lazy pipeline properties and requires_safety_checker-based safety gating
* Drop callback_on_step_end from Cosmos3 denoise loop
* Move container/auto blocks into modular_blocks
* Move action_gen check, remove unused params
* Declare video_processor as ComponentSpec; drop unused pipeline state
* Split VAE encode block by modality (image and video)
* Remove Cosmos3AssembleResultStep; add Cosmos3ExportStep
* Remove unused action_mode
* Refactor Cosmos3 modular denoising by modality
* Document Cosmos3 modular output selection
* Address Cosmos3 modular review feedback
* Remaining local-variable device cleanup
* Address Cosmos3 modular review feedback
* Address final Cosmos3 modular feedback
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Co-authored-by: Atharva Joshi <atjoshi@nvidia.com>
