vulkan: enable coopmat2 FA gqa and split_k optimizations more often

[jeffbolznv]

The grouped query attention optmization doesn't require a power of two ratio, the only thing relying on it was the modulo operation written as bitwise &.

split_k need not depend on gqa_ratio - enable it any time there's only one workgroup in the X dimension. The shader gets the split index from the x coord, and multiple workgroups in the X dimension (pre-split) indicates a larger FA operation that wouldn't need splitting.

Perf results:

before:

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -m C:\models\second-state\StarCoder2-7B-GGUF\starcoder2-7b-Q4_0.gguf -m C:\models\Qwen2-VL-7B-Instruct-IQ4_NL.gguf -m C:\models\Phi-3-mini-4k-instruct-q4.gguf -fa 1 -p 0 -n 8192 --repetitions 1
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 4070 (NVIDIA) | uma: 0 | fp16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |          test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | ------------: | -------------------: |
| starcoder2 7B Q4_0             |   3.76 GiB |     7.17 B | Vulkan     |  99 |  1 |        tg8192 |         55.98 ± 0.00 |
| qwen2vl 7B IQ4_NL - 4.5 bpw    |   4.13 GiB |     7.62 B | Vulkan     |  99 |  1 |        tg8192 |         57.88 ± 0.00 |
| phi3 3B Q4_K - Medium          |   2.23 GiB |     3.82 B | Vulkan     |  99 |  1 |        tg8192 |         68.98 ± 0.00 |

after:

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -m C:\models\second-state\StarCoder2-7B-GGUF\starcoder2-7b-Q4_0.gguf -m C:\models\Qwen2-VL-7B-Instruct-IQ4_NL.gguf -m C:\models\Phi-3-mini-4k-instruct-q4.gguf -fa 1 -p 0 -n 8192 --repetitions 1
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 4070 (NVIDIA) | uma: 0 | fp16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |          test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | ------------: | -------------------: |
| starcoder2 7B Q4_0             |   3.76 GiB |     7.17 B | Vulkan     |  99 |  1 |        tg8192 |         74.72 ± 0.00 |
| qwen2vl 7B IQ4_NL - 4.5 bpw    |   4.13 GiB |     7.62 B | Vulkan     |  99 |  1 |        tg8192 |         74.87 ± 0.00 |
| phi3 3B Q4_K - Medium          |   2.23 GiB |     3.82 B | Vulkan     |  99 |  1 |        tg8192 |         77.90 ± 0.00 |

(This qwen model seems to be broken at TOT, even with the cuda backend, but the speedup is probably realistic)