Specdec Bench: vLLM reqid, SGL path, conc > 1 metric fix

[IzzyPutterman]

What does this PR do?

SGLang Fix for actually passing the draft model path to the engine

vLLM Fix for multiturn to not overlap request_id strings

Acceptance Rate Fix for potential race condition on multiturn datasets in writing back AR

Overview: ?

Usage

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Testing

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Additional Information

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.37%. Comparing base (7d0f7a9) to head (1f7e8cb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #541   +/-   ##
=======================================
  Coverage   74.37%   74.37%           
=======================================
  Files         182      182           
  Lines       18219    18219           
=======================================
  Hits        13550    13550           
  Misses       4669     4669           

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[yeyu-nvidia]

Can you add some description of this PR?

[IzzyPutterman]

Can you add some description of this PR?

Updated the description

[h-guo18]

LGTM