1. ConstantValue
* just holds some value and its type
* implementations for concrete constants
2. CompileTimeConstant
* is only produced by ConstantExpressionEvaluator
* has additional flags (canBeUsedInAnnotation etc)
* has two implementations TypedCompileTimeConstant containing a constant value
and IntegerValueConstant which does not have exact type
* can be converted to ConstantValue
Adjustt usages to use ConstantValue if flags are not needed
Add tests for some uncovered cases