Support vulkan shaderStorageImage{Read/Write}WithoutFormat

[Vecvec]

Is your feature request related to a problem? Please describe.
Having to write the texel format in a shader limits it's usage, and with compute based ray-tracers (especially if a library wants to simply provide a generic shader) this can be an inconvenience. This means the texel format cannot be selected by the user.

Describe the solution you'd like
A wgpu feature for vulkan's shaderStorageImage{Read/Write}WithoutFormat extensions (either combined or seperate, for RT it probably doesn't matter). Both DirectX12 and Metal always support this.

Describe alternatives you've considered
It's not too hard to take a texture and convert it to another using a compute shader.

Additional context
See gpuweb/gpuweb#4298