Results 2 issues of fox34

Explicitly denote classes that implement __toString as Stringable (as [suggested by the official PHP docs](https://www.php.net/manual/en/class.stringable.php)), which helps IDEs to check type safety.

As discussed in #7334. Thank you @Smanar! - Product name : TRVZB - Manufacturer : SONOFF - Model identifier : TRVZB

Device Request