This allows to declare SRV buffers in the shader tests using `[buffer srv n]` blocks, and passing them to the different backends.
Also, 1/2 includes a missing bit required to parse `Buffer<>` types in the HLSL compiler.
This is a step towards supporting StructuredBuffer types in further patches.
-- v4: tests/shader-runner: Change probe directive syntax on shader_test files. tests/shader-runner: Change resource declaration syntax on shader_test files. tests/shader_runner: Support SRV buffers. tests/shader-runner: Separate resource_type into type and dimension.