A helper class to assist with lazy loading of Primitives.
The primitive's textual name.
The fully qualified name of the Primitive subclass.
The full name of the Java class implementing the primitive.
The name by which a primitive function is declared in Avail code.
The sole instance of the specific subclass of Primitive. It is initialized only when needed for the first time, since that causes Java class loading to happen, and we'd rather smear out that startup performance cost.