Support is/as/as? with Function[K]<...> types.

compiler/testData/codegen/boxWithJava/casts/javaTypeIsFunK/JFun.java

@@ -0,0 +1,5 @@
+class JFun implements kotlin.jvm.functions.Function0<String> {
+    public String invoke() {
+        return "OK";
+    }
+}

compiler/testData/codegen/boxWithJava/casts/javaTypeIsFunK/javaTypeIsFunK.kt

@@ -0,0 +1,6 @@
+fun box(): String {
+    val jfun = JFun()
+    val jf = jfun as Any
+    if (jf is Function0<*>) return jfun()
+    else return "Failed: jf is Function0<*>"
+}