Optimistically add isInstance and qualifiedName to common KClass

Because they are used in common cast and safeCast functions

libraries/stdlib/src/kotlin/reflect/KClass.kt

@@ -19,4 +19,17 @@ public expect interface KClass<T : Any> {
      * or `null` if the class has no name (if, for example, it is an anonymous object literal).
      */
     public val simpleName: String?
+
+    /**
+     * The fully qualified dot-separated name of the class,
+     * or `null` if the class is local or it is an anonymous object literal.
+     */
+    public val qualifiedName: String?
+
+    /**
+     * Returns `true` if [value] is an instance of this class on a given platform.
+     */
+    @SinceKotlin("1.1")
+    public fun isInstance(value: Any?): Boolean
+
 }