[model] feat: support parameter generator for model engine

[vermouth1992]

What does this PR do?

• Support parameter generator for model engine
• Add tests for Qwen3 and Qwen3MoE

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[gemini-code-assist]

Code Review

This pull request introduces a parameter generator for model engines and adds corresponding tests. The implementation for FSDP and Megatron engines has been added. My review focuses on correctness and consistency in these new engine implementations.

I've identified a critical issue in the FSDP engine implementation where state_dict() is called without the necessary context, which could lead to incorrect behavior with sharded models. Additionally, there's a high-severity issue in the Megatron engine implementation regarding inconsistent parameter offloading logic compared to the FSDP engine, which could cause GPU memory issues. The refactoring in the actor and critic roles looks good.