First part of v2 of !38, trying to follow the wide feedback provided.
Following patches in: https://gitlab.winehq.org/fcasas/vkd3d/-/tree/documentation
-- v2: vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_src. vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_ir_node. vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_ctx. vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_ir_var. vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_struct_field. vkd3d-shader/hlsl: Add field-level documentation to struct hlsl_type. vkd3d-shader/hlsl: Rename hlsl_struct_field.modifiers to "storage_modifiers". vkd3d-shader/hlsl: Rename hlsl_ir_var.modifiers to "storage_modifiers".