* add bool cwhn = true to conv_2d test cases
* add layout check at graph building time
* extend layout checks for conv2d.cu kernel
* in CPU back-end kernel needs to be stored contiguously to prevent test failures with cwhn=1
* trim white space
* do op support check in vulkan backend
* fix CI failure and vulkan run-time assert failure by introducing new graph build-time check in ggml_backend_vk_device_supports_op
* add additional check in support_op function for Vulkan to fix run-time assert failure
