Describe the pull request

This PR introduces a new PipelineBindingHint structure that can be passed to shader reflection in order to control aspects of the resulting pipeline layout that can not be implicitly inferred from the shader metadata. Currently this includes:

• Turning a descriptor set into a push constant range. This is especially helpful for the D3D12 backend, as it removes the need to define explicit root signatures in the shaders.
• Providing a static/immutable sampler state to sampler bindings. This works for both backends. In D3D12 this removes the need to define a root signature in the shader. In Vulkan, this was previously impossible without explicitly defining the pipeline layout.
• Providing a upper limit for the descriptor count of unbounded arrays. This is especially helpful for the Vulkan backend, where one would frequently run into different validation errors, as the descriptor count of an unbounded array still counts towards the device limits, even if the actual allocated memory is managed independently from this after Use descriptor buffers to implement descriptor management for Vulkan. #163. Setting the descriptor count to a low number instead does not work either, as the driver reserves address space based on the descriptor count. With this addition, clients gain better control over the individual array definitions without having to explicitly define the whole pipeline layout.

Additionally, hints serve as a rudimentary validation logic. They are used to communicate "intend", so if the layout deviates from this expressed intend, diagnostic log messages (mostly warnings) will be issued.

Related issues

• Towards Add support for dynamic descriptor types and direct heap access. #164
• Closes Add binding hints to shader reflection for unsupported scenarios. #167