For example, `java.util.ArrayList.elementData` is a generic
package-private method. Not unwrapping intersection/substitution fake
overrides resulted in incorrect FQ names being compared in the package
visibility check, which led to the fake override always being created in
any subclass of ArrayList.
This change will help in testing IR fake overrides (KT-61360) because in
the current (temporary) mode, IrFakeOverrideRebuilder throws an
exception if initial fake overrides constructed by fir2ir differ from
the ones rebuilt by the IR -- and here they'll be different after fixing
KT-61366.