This structure should only be created by the RendererMain's createShader
method. The structure is immutable and should not be modified once created.
A ShaderRef exists in the Main API Space and is used to point to an actual
Shader instance in the Core API Space. The ShaderRef is used to
communicate with the Core API Space to create, load, and destroy the
Shader instance.
This type is technically a discriminated union of all possible shader types.
If you'd like to represent a specific shader type, you can use the
SpecificShaderRef generic type.
An immutable reference to a Shader