FIR: Implement fast path for classes subtyping

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirSession.kt

@@ -19,6 +19,7 @@ abstract class FirSession(val sessionProvider: FirSessionProvider?) {
 
     var _firSymbolProvider: Any? = null
 
+    var _correspondingSupertypesCache: Any? = null
 
     fun <T : Any> getService(kclass: KClass<T>): T =
         components[kclass] as T
@@ -34,4 +35,4 @@ interface FirSessionProvider {
 }
 
 inline fun <reified T : Any> FirSession.service(): T =
-    getService(T::class)
+    getService(T::class)