JavacSourcePosition's documentation says: "Implementation of model API SourcePosition based on javac internal state." That model API class does not exist, and the methods are never used in javac. They can be removed.

`getSourcePosition(Element, AnnotationMirror, AnnotationValue)` was never implemented, and has a matching TODO to `getTreeAndTopLevel(Element, AnnotationMirror, AnnotationValue) ` (see JDK-6388543).