Fix htaccess files for PHP 8

Problem/Motivation

We need to add PHP 8 stuff to .htaccess files because there is php7 stuff.

Proposed resolution

Add checks for mod_php.c - PHP has changed the module name so we don't have to do this in the future. Yay. See https://www.php.net/manual/en/migration80.other-changes.php - php7_module has been renamed to php_module.

Remaining tasks

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

The root .htaccess file now has a section for PHP 8 settings. This brings .htaccess files into alignment with Drupal's supported PHP version.

If you have a custom .htaccess file and its PHP settings are working, you can keep using your existing .htaccess file unchanged. If you are upgrading from PHP 7 to PHP 8, you should copy the custom settings that you need from the PHP 7 section to the PHP 8 section.