Replace builders with descriptor structures

[Kangz]

WebGPU will use descriptor structures to pass all the arguments required for the creation of objects. Match this for all objects.

• BindGroup
• BindGroupLayout (PR: Use a descriptor for BindGroupLayout #211)
• Buffer
• ComputePipeline
• PipelineLayout (PR: Use a descriptor for PipelineLayout #206)
• CommandBufferBuilder::BeginRenderPass
• RenderPipeline
  • Make the pipeline descriptor monolithic #201 Make render pipeline descriptor monolithic
• ShaderModule
• Texture
• Sampler (PR: Sampler descriptor #195)