FPM: Freeing child allocated data

Description

FPM allocates some data during child initialization for keeping around some configuration options. This is done in following places:

• https://github.com/php/php-src/blob/15184435007ae13d31902be2613632b813b80b0f/sapi/fpm/fpm/fpm_log.c#L81 (this was reported in https://bugs.php.net/bug.php?id=75635 and it is the reason for creating this issue).
• https://github.com/php/php-src/blob/15184435007ae13d31902be2613632b813b80b0f/sapi/fpm/fpm/fpm_log.c#L91
• https://github.com/php/php-src/blob/15184435007ae13d31902be2613632b813b80b0f/sapi/fpm/fpm/fpm_status.c#L32
• https://github.com/php/php-src/blob/15184435007ae13d31902be2613632b813b80b0f/sapi/fpm/fpm/fpm_status.c#L40-L41
• https://github.com/php/php-src/blob/15184435007ae13d31902be2613632b813b80b0f/sapi/fpm/fpm/fpm_php.c#L219-L221 (this just takes ownership but means the same sort of leak effectively)

Those values are never freed. They are needed for the whole life of child so it is not a big issue as it gets released on process exit (that's why this is classified more as a feature and not a bug because there is no impact of this). However it is a good convention to free those values so some child destroy functions should be created for that purpose and called before exiting the child.

Start by reading the child-initialization code in sapi/fpm/fpm/fpm_log.c, fpm_status.c, and fpm_php.c, then trace the child exit path. Add corresponding child-destroy handling for the allocations listed in the issue and call it before the child exits. Done means those child-owned values are freed during shutdown rather than only at process exit.