FIC: support fun interfaces in stub builder

idea/testData/decompiler/decompiledText/FunInterfaceDeclaration/FunInterfaceDeclaration.kt

@@ -0,0 +1,13 @@
+package test
+
+class FunInterfaceDeclaration {
+    @Suppress("UNSUPPORTED_FEATURE")
+    fun interface KRunnable {
+        fun invoke()
+    }
+
+    @Suppress("UNSUPPORTED_FEATURE")
+    fun interface GenericKRunnable<T, R> {
+        fun invoke(t: T): R
+    }
+}