feat: enable FP8 large-head attention on SM80

[jhaotingc]

📌 Description

🔍 Related Issues

🚀 Pull Request Checklist

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🧪 Tests

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🔬 Experimental Track

• This PR is experimental: it adds or changes code under flashinfer/experimental/ and/or an @flashinfer_experimental_api. Tracking issue: #
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  • Tests live in tests/experimental/ and were validated on the intended hardware; a runnable example is included.
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# One target per line: a directory or a file. (A pytest ::selector is not
# supported -- the sharding runner cannot consume one.) Must be under
# tests/experimental/ and must exist. Delete these comment lines and add yours, e.g.
#
#   tests/experimental/test_my_backend.py
#   tests/experimental/my_backend/
#
# Declaring the whole tree (tests/experimental/) is allowed but means every
# experimental PR pays for every other feature's tests, in every matrix cell.

Reviewer Notes

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