Remove support for primitive classes in the compiler:
 - switches for checking if primitive classes are allowed and code protected by them
 - remove flavors, Q-types, primitive classes related predicates
 - uses of `.ref` `.val` and projections related code
 - parser support for primitive classes
 - removing the PRIMITIVE_CLASS and ACC_PRIMITIVE flags and its uses
 - some minor refactorings and adjustments to regression tests
 - removing Type.ConstantPoolQType