[Opt] Add fused triton operator for MLA models to gsa_on_device

[Fengli5355]

Purpose

Fuse hash and cache operators for MLA sparse module.

Modifications

1. Implemented a fused hash and concat-cache MLA kernel. This optimization avoids storing intermediate results to HBM, reducing GPU memory I/O and improving execution efficiency with a single kernel launch.
2. Add unit test of the mla hash-and-cache fused operator.
3. Rename unit test of the gqa hash-and-cache fused operator.

Test

Test on DeepSeek-R1-awq with H100x8. TPOT is improved slightly.