Constant Value Checker: eliminate @StaticallyExecutable annotation and statically-executable.astub file

The annotation @StaticallyExecutable is not needed.

Instead, the Constant Value Checker should use any @Pure method whose argument and return types are all:

• primitives
• primitive wrappers
• Strings, CharSequence, and other immutable types to be indentified later
• arrays of the above

Once this is done, the file statically-executable.astub is no longer needed, or at least the JDK parts of it can be eliminated. (Make sure anything that it marked as @StaticallyExecutable is @Pure in the annotated JDK.)

Start by reading the Constant Value Checker implementation and the statically-executable.astub file, then inspect the annotated JDK declarations marked @StaticallyExecutable. Verify that those declarations are @Pure and determine which supported immutable types and array signatures are covered. Done means the annotation is eliminated and the JDK portions of the stub file are no longer needed.