[Flashinfer][gpt-oss] Support FP8-qkv Flashinfer TRTLLM Sinks Attention

[elvischenv]

Purpose

Support FP8-qkv Flashinfer TRTLLM sinks attention.
Note: require flashinfer v0.4.0rc4(updating in #26326)
flashinfer-ai/flashinfer#1758

Test Plan && Test Result

Kernel unit test:

tests/kernels/attention/test_flashinfer_trtllm_attention.py

===== 224 passed, 16 skipped in 30.94s ====

E2E accuracy:

kv_cache_dtype=fp8

[{'eval_name': 'gpqa', 'model_name': 'gpt-oss-120b-high_temp1.0_20250925_081936', 'metric': 0.7904040404040404}]
[{'eval_name': 'aime25', 'model_name': 'gpt-oss-120b-high_temp1.0_20250925_084243', 'metric': 0.925}]

kv_cache_dtype=auto

[{'eval_name': 'gpqa', 'model_name': 'gpt-oss-120b-high_temp1.0_20250925_090839', 'metric': 0.7910353535353535}]
[{'eval_name': 'aime25', 'model_name': 'gpt-oss-120b-high_temp1.0_20250925_093344', 'metric': 0.9125}]

E2E perf:

kv_cache_dtype=fp8, 6.9% perf gain

Output token throughput (tok/s):         22427.23

kv_cache_dtype=auto

Output token throughput (tok/s):         20977.07

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @elvischenv.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[nvpohanh]

@elvischenv Please fix the conflict. thanks!