Upgrade to PHP 8.1.5
Summary:
PHP 8.1 will allow to build tools and CI images with recent interpreter.
Bump Oniguruma version to 6.9.8.
Reference: https://www.php.net/ChangeLog-8.php#8.1.5
Ref T1725
Test Plan:
docker build .
docker run -it --rm hashnbr bash
php -i => and check if everything is okey
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T1725
Differential Revision: https://devcentral.nasqueron.org/D2678