Vulkan Flash Attention Coopmat1 Refactor (llama/19075)

Vulkan Flash Attention Coopmat1 Refactor (llama/19075)

* vulkan: use coopmat for flash attention p*v matrix multiplication

* fix P loading issue

* fix barrier position

* remove reduction that is no longer needed

* move max thread reduction into loop

* remove osh padding

* add bounds checks and padding

* remove unused code

* fix shmem sizes, loop duration and accesses

* don't overwrite Qf, add new shared psh buffer instead

* add missing bounds checks

* use subgroup reductions

* optimize

* move bounds check, reduce barriers

* support other Bc values and other subgroup sizes

* remove D_split

* replace Of register array with shared memory Ofsh array

* parallelize HSV across the rowgroups

* go back to Of in registers, not shmem

* vectorize sfsh

* don't store entire K tile in shmem

* fixes

* load large k tiles to shmem on Nvidia

* adapt shared memory host check function to shader changes

* remove Bc 32 case

* remove unused variable

* fix missing mask reduction tmspsh barrier

* fix mask bounds check

* fix rowmax f16 under/overflow to inf

* fix flash_attn_cm2 BLOCK_SIZE preprocessor directives