PR #11967: [XLA:GPU] Add cuDNN flash attention dbias computation and broadcast bias
PR #11967: [XLA:GPU] Add cuDNN flash attention dbias computation and broadcast bias

Imported from GitHub PR https://github.com/openxla/xla/pull/11967

* add cuDNN flash attention dbias computation. make sure dbias only pattern match cases where reduction is done on batch dim. Only bias with [1, N, S, T] is supported.
* add cuDNN broadcast bias support. cuDNN supports broadcast bias, [1, N, S, T], [1, 1, S, T] and [B, 1, S, T] are supported.
Copybara import of the project:

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0b3c19fba294402b735c1dc091cc57a955f5f334 by cjkkkk <ske@nvidia.com>:

add dbias

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2d9256c7f4c441824a831f2238ff7fdf2447f7f9 by cjkkkk <ske@nvidia.com>:

remove extra ()

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31750864e1bbf677cd82a8d4300fdb0a90d86e41 by cjkkkk <ske@nvidia.com>:

directly use rewriter result

Merging this change closes #11967

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/11967 from Cjkkkk:flash_attention_dbias 31750864e1bbf677cd82a8d4300fdb0a90d86e41
