Report error when referencing class name from decorator

[rbuckton]

This modifies the checker to report an error when referencing a class name from a decorator in that class when it is used immediately, i.e.:

@dec(C) // error
class C {}

@dec(() => C) // ok
class C {}

@dec((() => C)()) // error (IIFE indicates immediate use)
class C {}

This applies to decorators on all elements.

Fixes #57366