Use S6 instead of chaperone

Dockerfile

-FROM registry.git.autistici.org/ai3/docker/apache2-base:bullseye
+FROM registry.git.autistici.org/ai3/docker/apache2-base:s6
 
 COPY conf /tmp/conf
 COPY build.sh /tmp/build.sh

conf/chaperone.d/fpm.conf

-fpm-setup.service: {
-    command: "/bin/mkdir -p /run/php",
-    service_groups: INIT,
-    type: oneshot,
-}
-fpm.service: {
-    command: "/usr/sbin/php-fpm7.4 --force-stderr --nodaemonize",
-    exit_kills: true,
-}
-fpm-exporter.service: {
-    command: "sh -c '. /etc/apache2/envvars && HOME=/ exec /usr/sbin/php-fpm-exporter server --phpfpm.scrape-uri=unix:///run/php/php7.4-fpm.sock\\;/status --web.listen-address=:$PHP_FPM_EXPORTER_PORT'",
-    restart: true,
-}

conf/services.d/php-fpm-exporter/run

+#!/bin/sh
+. /etc/apache2/envvars
+export HOME=/
+exec /usr/sbin/php-fpm-exporter server --phpfpm.scrape-uri=unix:///run/php/php7.4-fpm.sock\\;/status --web.listen-address=:$PHP_FPM_EXPORTER_PORT

conf/services.d/php-fpm/finish

+#!/usr/bin/execlineb -S0
+
+s6-svscanctl -t /var/run/s6/services

conf/services.d/php-fpm/run

+#!/bin/sh
+mkdir -p /run/php
+exec /usr/sbin/php-fpm7.4 --force-stderr -nodaemonize