vulkan: optimizations for direct convolution (#14933)

vulkan: optimizations for direct convolution (#14933)

* vulkan: optimizations for direct convolution

- Empirically choose a better tile size. Reducing BS_K/BS_NPQ helps fill
  the GPU. The new size should be amenable to using coopmat, too.
- Fix shmem bank conflicts. 16B padding should work with coopmat.
- Some explicit loop unrolling.
- Skip math/stores work for parts of the tile that are OOB.
- Apply fastdiv opt.
- Disable shuffles for NV.

* Three tiles sizes for CONV_2D, and a heuristic to choose

* reallow collectives for pre-Turing

* make SHMEM_PAD a spec constant

* fixes for intel perf - no shmem padding, placeholder shader core count

* shader variants with/without unrolling

* 0cc4m's fixes for AMD perf

Co-authored-by: 0cc4m <redacted>
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Co-authored-by: 0cc4m <redacted>