Add array_is_list(array $array) function

This function tests if an array contains only sequential integer keys. While
list isn't an official type, this usage is consistent with the commu

Add array_is_list(array $array) function

This function tests if an array contains only sequential integer keys. While
list isn't an official type, this usage is consistent with the community usage
of "list" as an annotation type, cf.
https://psalm.dev/docs/annotating_code/type_syntax/array_types/#lists

Rebased and modified version of #4886

- Use .stub.php files
- Add opcache constant evaluation when argument is a constant
- Change from is_list(mixed $value) to array_is_list(array $array)

RFC: https://wiki.php.net/rfc/is_list

Co-Authored-By: Tyson Andre <tysonandre775@hotmail.com>
Co-Authored-By: Dusk <dusk@woofle.net>

Closes GH-6070

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