[php-src] Issue #11327: Expose time spent collecting cycles in `gc_status()`

Issue: https://github.com/php/php-src/issues/11327 Author: sebastianbergmann ### Description I had a conversation with @Girgias recently about whether it would be possible to retrieve the amount of time spent collecting cycles from userland. He told me that I should probably talk to somebody else. @edorian told me that the information is available in the Zend Observer API and that it should be almost trivial to make it available to userland. However, @beberlei tod me that using the Zend Observer API is not required for this. Instead, he proposes to introduce a global variable that counts the time spent in collecting cycles and "just" expose that as part of gc_status()' result. **TL;DR:** I would like information on time spent collecting cycles to be part of the array returned by gc_status().