Enable FusedSDPA for prompt attention with VLLM_PROMPT_USE_FUSEDSDPA

[libinta]

The current baseline doesn't have chunked prefill enable, it has oom for llama3-8b with 20k input. This change fixes it. Also it has performance benefit to utilize scaled_masked_triangular_softmax_fwd_hf8 kernel for long prompt.
Accuracy test also passes
the test passed. accuracy is preserved:
before change: /job/vLLM/job/single-scenario/709/console
"accuracy": 106.85
"performance": 391.4
after change: /job/vLLM/job/single-scenario/710/console
"performance": 393.3
"accuracy": 106.89,
small acc deviations are expected.
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FIX #xxxx (link existing issues this PR will resolve)

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[kdamaszk]

LGTM