Create Pipeline Layouts from Shader Reflection

[crud89]

Describe the pull request

This PR adds support for creating pipeline layouts from shader reflection. Currently pipeline layouts need to be explicitly defined in code:

SharedPtr<ShaderProgram> shaderProgram = device->buildShaderProgram()
    .withVertexShaderModule("shaders/basic_vs." + FileExtensions<TRenderBackend>::SHADER)
    .withFragmentShaderModule("shaders/basic_fs." + FileExtensions<TRenderBackend>::SHADER)); 

UniquePtr<RenderPipeline> renderPipeline = device->buildRenderPipeline(*renderPass, "Pipeline")
    .layout(device->buildPipelineLayout()
        .descriptorSet(DescriptorSets::Constant, ShaderStage::Vertex | ShaderStage::Fragment)
            .withUniform(0, sizeof(CameraBuffer))
            .add()
        .descriptorSet(DescriptorSets::PerFrame, ShaderStage::Vertex)
            .withUniform(0, sizeof(TransformBuffer))
            .add())
    .shaderProgram(shaderProgram);

With this PR, it is possible to generate a layout directly from the shader program by calling reflectPipelineLayout on it:

SharedPtr<ShaderProgram> shaderProgram = device->buildShaderProgram()
    .withVertexShaderModule("shaders/basic_vs." + FileExtensions<TRenderBackend>::SHADER)
    .withFragmentShaderModule("shaders/basic_fs." + FileExtensions<TRenderBackend>::SHADER)); 

UniquePtr<RenderPipeline> renderPipeline = device->buildRenderPipeline(*renderPass, "Pipeline")
    .layout(shaderProgram->reflectPipelineLayout())
    .shaderProgram(shaderProgram);

Additionally, in DirectX, it is not possible to define input attachments as subpass references. Instead the engine automatically defines a static sampler at register s0 of space 0. With reflection, render targets are being treated as normal texture descriptors, since it is not possible to tell them apart based on their usage. The static sampler, however, is currently not supported to be de-serialized. To solve this, the pipeline layout is improved with support for static samplers.

Related issues

• Fixes Allow descriptor set to be build from shader reflection #5.
• Fixes Support static/immutable Samplers #69.

A designated topic regarding shaders can be found in the project wiki.