[php-src] Issue #8038: DOM extension reflection version is incorrect

Issue: https://github.com/php/php-src/issues/8038 Comment Author: cmb69 @alecpl, few years ago most bundled extensions switched to using the PHP_VERSION, because it is hard to track their own versioning. Still it makes sense to have an own version for all extensions, just in case they will be unbundled (and moved to PECL) in the future, so they would need their own versioning. Maybe we could remove DOM_API_VERSION in PHP 8.2, but that would be a BC break, and I'm not sure whether that would be appropriate for a minor version, given the small gain. And it wouldn't solve the issue we're having now (in PHP 8.0 and 8.1).