Redefined buffer types

[jaebaek]

AmberScript's buffer type is confusing.

I feel that we should have the following buffer types:

• color for color attachment of framebuffer
• depth stencil for depth/stencil attachment of framebuffer
• vertex for vertex buffer
• index for index buffer
• storage image
• sampled image
• combined image sampler
• uniform texel buffer
• storage texel buffer
• storage buffer
• uniform buffer
• input attachment

Note that here we also uses the term 'buffer' for image because in the view of Amber script, the image is also a sequence of bytes.

Since storage image, sampled image, combined image sampler, uniform texel buffer, storage texel buffer, storage buffer, uniform buffer, and input attachment are Vulkan specific descriptor types and I am not sure WebGPU will define the same types or not, we would better consider how to support buffers of WebGPU efficiently.

[dj2]

For things like storage image and storage sampled, does the different matter from the Amber perspective? It's a bunch of contiguous bits. Do we need separate buffer types for them? Does the difference between storage image and storage buffer matter at the AmberScript level? How you use it on the backend would make that destinction, no?

[jaebaek]

As we discussed in offline, an alternative is to separate the type from buffer and add the type argument for DESCRIPTOR_SET command. In that way, the buffer is just a data blob and we can also run WebGPU resource types with the same data.

[dj2]

This was done in #66