[Doc]: Missing docstrings for CachedModelLoader methods in tensorrt_llm/llmapi/llm_utils.py

📚 The doc issue

The CachedModelLoader class in tensorrt_llm/llmapi/llm_utils.py is missing docstrings on four of its members, while the neighboring ModelLoader class and the module-level helper functions in the same file are documented.

Undocumented members:

• CachedModelLoader.__init__
• CachedModelLoader.workspace (property)
• CachedModelLoader._submit_to_all_workers
• CachedModelLoader.__call__

__call__ in particular carries non-obvious behavior worth documenting: it downloads the speculative model when one is configured, short-circuits for the _autodeploy backend, and returns a (None, hf_model_dir) tuple whose first element is always None. Readers currently have to trace the body to learn any of this.

This is a documentation-only gap; no functional change is involved.

Suggest a potential alternative/fix

Add Google-style docstrings to the four members listed above, matching the style already used by ModelLoader and the module-level helpers in the same file.

I'd like to work on this and open a PR.

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