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.

まず sapi/fpm/fpm/fpm_log.c、fpm_status.c、fpm_php.c の子プロセス初期化コードを読み、続いて子プロセスの終了経路を追跡します。issue に記載されているアロケーションに対応する子プロセス破棄処理を追加し、子プロセスが終了する前に呼び出します。これらの子プロセス所有の値がプロセス終了時だけでなく、シャットダウン中に解放されれば完了です。