[JS IR BE] Implement type check

* IrTypeOperator lowering
 * runtime support
 * refactoring

core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java

@@ -944,6 +944,10 @@ public abstract class KotlinBuiltIns {
         return classFqNameEquals(classDescriptor, FQ_NAMES._boolean);
     }
 
+    public static boolean isNumber(@NotNull KotlinType type) {
+        return isConstructedFromGivenClassAndNotNullable(type, FQ_NAMES.number);
+    }
+
     public static boolean isChar(@NotNull KotlinType type) {
         return isConstructedFromGivenClassAndNotNullable(type, FQ_NAMES._char);
     }