[trainer] fix: resolve dataset config in agent loop

[yyDing1]

What does this PR do?

line 516: dataset_config=self.config.data

https://github.com/volcengine/verl/blob/772c224935d136b05f5f2d10ddaa6d3b7a41403c/verl/experimental/agent_loop/agent_loop.py#L509-L517

self.config.data may have unresolved arguments like 'tool_config_path': '${oc.select:actor_rollout_ref.rollout.multi_turn.tool_config_path, null}', which cannot be instantiated. This will cause error

*** omegaconf.errors.InterpolationResolutionError: TypeError raised while resolving interpolation: Index 'actor_rollout_ref' (str) is not an int

Solution:

Wrap it in DictConfigWrap, so that it will not be initialized in hydra resolve config.

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[gemini-code-assist]

Code Review

This pull request correctly resolves an OmegaConf interpolation error by wrapping the dataset_config in a DictConfigWrap class to prevent premature resolution by Hydra. The changes are consistent and effectively address the issue. I've also identified a critical race condition in the AsyncLLMServerManager that is closely related to the code being changed and should be addressed.