Fix creating of refined FlexibleType and RawType

There was an issue that `KotlinType.equals` called in `KotlinTypeFactory.flexibleType`
  and `RawType` constructor produced endless recursion of types that wasn't
  computed yet

core/descriptors/src/org/jetbrains/kotlin/types/flexibleTypes.kt

@@ -139,9 +139,10 @@ class FlexibleTypeImpl(lowerBound: SimpleType, upperBound: SimpleType) : Flexibl
 
     @TypeRefinement
     @UseExperimental(TypeRefinement::class)
-    override fun refine(kotlinTypeRefiner: KotlinTypeRefiner) =
-        KotlinTypeFactory.flexibleType(
+    override fun refine(kotlinTypeRefiner: KotlinTypeRefiner): FlexibleType {
+        return FlexibleTypeImpl(
             kotlinTypeRefiner.refineType(lowerBound) as SimpleType,
             kotlinTypeRefiner.refineType(upperBound) as SimpleType
-        ) as FlexibleType
+        )
+    }
 }