Shader VUIDs that really belong to draw calls

`VkPipelineShaderStageCreateInfo` has some VUIDs that can't really be validated:
- VUID-VkPipelineShaderStageCreateInfo-stage-02596
- VUID-VkPipelineShaderStageCreateInfo-stage-02597
- VUID-VkPipelineShaderStageCreateInfo-stage-06685
- VUID-VkPipelineShaderStageCreateInfo-stage-06686

The behaviour of the shader regarding these variables can depend on the inputs to the shader, so it's not known at the time a pipeline is created. They can only be known when all inputs are known, which is at draw time.

Review VUIDs 02596, 02597, 06685, and 06686 for VkPipelineShaderStageCreateInfo, then trace where their conditions depend on draw inputs. Determine how the specification should represent these requirements at draw time; done means the VUIDs are assigned to the appropriate validation point and the affected wording is consistent.

Written by the indexing model from the issue text.