This PR was squashed before being merged into the 1.23-dev branch.

Discussion
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[Php81] Optimize `array_is_list`

Hey there,

I've used this function quite a lot and I see a massive performance gap between [webmozart/assert](https://github.com/webmozarts/assert/blob/f07851c5b43e4cb502c24068620e9af6cbdd953f/src/Assert.php#L1823) and this polyfill.
https://3v4l.org/ruYVL

This polyfill covers a niche case with `\NAN` and thus, my previous attempt in #355 failed.

So I've worked out another solution which is still a little bit faster than the current one.
https://3v4l.org/KiCg2

Commits
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8cc03ca [Php81] Optimize `array_is_list`

…n related class stubs. (Firtzberg)

This PR was merged into the 1.23-dev branch.

Discussion
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[PHP 8.1] [PHP 7.3] Preventing redeclaration of PHP version related class stubs.

Same as symfony/polyfill#359, only for other PHP version related class stubs.

Commits
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4cddf20 Preventing redeclaration of PHP version related class stubs.