[perf] fix: profiler bug fix for agent loop

[mengchengTang]

What does this PR do?

Updated Description: This PR fixes the missing rollout profiling data issue caused by the Agent Loop architecture shift.

Root Cause: Inference requests now bypass the generate_sequences method of the worker, causing missing performance data during the rollout phase in Discrete Mode.

Solution: We add explicit profiling control to support the current rollout workers. This is a backward-compatible fix. New methods start_capture_profile and stop_capture_profile in DistProfiler and Workers. AgentLoopManager now manually starts and stops profiling via vLLMReplica around inference requests.

This ensures existing rollout workers can collect performance data correctly.

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[tardis-key]

It can be seen that the overall process control and the actual profiling startup are far apart, and the original solution requires passing the calling function many times, which is not elegant enough.

[tardis-key]

@FightingZhen @wuxibin89 ready for review. This pr is bugfix for legacy_workers.

[tardis-key]

Is there any way to unify start_e2e_profiler and start_capture_profiler?