Even though SO may not be correct
overrides sometimes, it feels more
natural to treat fake overrides as...
well, "overrides". And without it
we'd need to make the code in
`FirOverrideChecker` less intuitive.
If a serializable class has generic type parameters, its serializer is not an object
and has a specialized constructor. This constructor was public in K1 and should
be public in K2 so it can be called from other serializable classes
(in case class is e.g., part of sealed hierarchy).
#KT-63402 Fixed