Vulkan Scalar Flash Attention Refactor (#19625)
* vulkan: allow using fp16 in scalar flash attention shader
* split rows inside of subgroups for faster synchronization
* use row_split when Br >= 4, change reductions to use shared memory if row_split == 1
* use f32 scalar FA if f16 is not supported by device
* fix amd workgroup size issue
* optimize masksh use
* add medium rows FA shader Br size
* fixes
* add padding to mask shmem buffer
* cache q values into registers for KQ
* fuse lf accumulation, pf and v accumulation into a loop
* stage K loads through shmem
* stage V loads through shmem
* only stage through shmem on Nvidia
* default to Bc 32
* also stage V through shmem when this is done for K
* dynamic subgroups for intel
* use vectorized stores
* use float_type for dequantize4 functions
* use smaller scalar rows size for smaller rows count
* relax flash attention split_k condition to allow non-gqa use
* use minimal subgroup size on Intel
* fix shmem support function
* fix rebase issues
* fixes
* Bc 4 for scalar FA is not a valid configuration
* Use wave32 on AMD RDNA for scalar FA
* add Intel shader core count lookup-table
* fix regressions
* device tuning
* tmpsh size fix
* fix editorconfig
* refactor fa tuning logic into a single place
* fix gqa opt logic
* fix block_rows with small n_rows
* amd tuning
* fix hsk=72/80 issue
* tuning
* allow condition skipping for column check
* use float16 for Of if available
* address feedback
* fix bad RDNA performance on head size <= 128 by limiting occupancy
* allow printing pipeline stats
* cleanup and fixes
* limit occupancy for GCN for small batch FA with large HSK
* disable f16 FA for GCN AMD GPUs on the proprietary driver
