Refined get_class and related function signatures.

[mad-briller]

https://www.php.net/manual/en/function.get-class.php

get_class can return false prior to php8.0

[ondrejmirtes]

Oh, I'm getting it back. There's already a return type extension for get_class() that's correct.

[ondrejmirtes]

Do you have a bug in mind where it doesn't work properly? Ideally reproduced on phpstan.org/try.