vulkan: implement several ops relevant for ggml_opt (#11769)
* vulkan: support memset_tensor
* vulkan: support GGML_OP_SUM
* vulkan: implement GGML_OP_ARGMAX
* vulkan: implement GGML_OP_SUB
* vulkan: implement GGML_OP_COUNT_EQUAL
* vulkan: implement GGML_OP_OPT_STEP_ADAMW
* vulkan: fix check_results RWKV_WKV6 crash and memory leaks
* vulkan: implement GGML_OP_REPEAT_BACK
* tests: remove invalid test-backend-ops REPEAT_BACK tests
* vulkan: fix COUNT_EQUAL memset using a fillBuffer command
