[Benchmark] Adding "facebook/opt-125m" model in the benchmarking tests for both vLLM and SGLang

[namanlalitnyu]

Changes:

• This PR involves adding facebook/opt-125m model in the benchmarking tests (serving, latency, and throughput) for both vLLM and SGLang frameworks.
• Based on our discussion, we need to remove the serving tests for qwen model for SGLang benchmarking.
• Fixing issue related to the SGLang benchmarks failing.

Testing:

• Github Action for SGLang benchmarking containing the facebook model: link
• Github Action for vLLM benchmarking containing the facebook model: link
• HUD Dashboard also showing the facebook model benchmarking results: link

[namanlalitnyu]

One of the Github actions for qwen model is failing, and its unrelated to our changes, as this PR doesn't touch the vllm-benchmark workflow, and also the test fails due to the vllm server not starting. Hence, we are good with merging these changes.