The existing code does not set the list of bases that
FirLightInterfaceClassSymbol extends for "extendsList". It collects only
the set of interfaces for "extendsList" of FirLightInterfaceClassSymbol.
However, interfaces can "extend" other classes and/or interfaces, but
they cannot "implement" other interfaces. Therefore, we have to includes
all interfaces and classes that the child interface extends in
the "extendsList". Additionally, this commit adds `private fun
PsiClass.hasSuper(..): Boolean` to FirLightClassBase that returns
whether one of recursive super classes of the PsiClass is `baseClass`
or not. This commit lets `isInheritor()` method use
`PsiClass.hasSuper()`.
Jaebaek Seo