[PHP 8.3] Add #[\Override] attribute

[IonBazan]

Adds #[\Override] attribute introduced in PHP 8.3: https://wiki.php.net/rfc/marking_overriden_methods

Failing tests are unrelated

[derrabus]

LGTM. Would it make sense to add a functional test? Like, using the attribute on a class and verify that we can load it via reflection?

[IonBazan]

@derrabus we don't usually do that as tests are using the autoloader generated from root composer.json, while symfony/polyfill-php83 dependants will use the sub-split with its own composer.json. I don't think we can test that easily but I agree it is quite prone to error.

[IonBazan]

Thanks for the review @nicolas-grekas - addressed the issues.

[nicolas-grekas]

I'd keep the constructor if it's on the native implem, so that the reflection info is as close as possible to the native one... (can you check this aspect ?)

[nicolas-grekas]

Thank you @IonBazan.