Fix image size (apt caches), fpm graceful stop, stop during startup and Apache modules

[mistraloz]

Summary

This PR fixes :

• Bug
• Feature
• Breaking changes

1. Image size: images built FROM a slim image got a ~110MB layer from the ONBUILD hook, even without any
   extension (PHP_EXTENSIONS empty), and fat images carried the same garbage. The install scripts disable the
   docker-clean apt configuration while installing: apt-get update then creates /var/cache/apt/pkgcache.bin and
   srcpkgcache.bin (~105MB) that apt-get clean no longer knows once docker-clean is restored.
   The hook now exits right away when PHP_EXTENSIONS is empty, and the caches are removed explicitly.
2. fpm graceful stop: STOPSIGNAL SIGQUIT (PHP-FPM completes the running requests) and EXPOSE 9000.
3. Stop requested while the container is starting: the stop signal was lost and the container was killed after
   the stop timeout (exit 137 after 10s). bash always ignores SIGQUIT (fpm) and ignores SIGWINCH (apache) by
   default. The entrypoint and apache2-foreground now trap them. SIGTERM/SIGINT (cli) are not trapped: they
   already stop bash right away (and trapping them would delay the stop until the end of a long startup command).
4. Apache modules: brotli, cern_meta, imagemap, md, proxy_hcheck, proxy_uwsgi and socache_redis are
   shipped by Ubuntu and documented as available, but were ignored (APACHE_EXTENSION_*) or rejected
   (APACHE_EXTENSIONS).
5. Minor: the sed commenting the default listen socket of www.conf did nothing (single quotes). No visible effect,
   zz-docker.conf already overrides listen.

/var/cache/apt (PHP 8.4, amd64):

Image	Before	After
FROM thecodingmachine/php:8.4-v5-slim-cli (ONBUILD, PHP_EXTENSIONS empty)	105 MB	12 kB
8.4-v5-cli (fat)	105 MB	12 kB

Related issues: #358 (slow shutdown, not reproducible on v5 anymore: 0.1-0.6 s, graceful now), #215 (Apache
SIGWINCH: after the initialization it already works on v5, the remaining case was a stop during the
initialization, fixed here).

Test plan (required)

New tests: test_gracefulStop and test_stopDuringStartup (fpm), test_stopDuringStartup and
test_enableApacheModule (apache).

TAG_PREFIX=pr1- docker buildx bake --load php84-slim-<variant> php84-<variant>
TAG_PREFIX=pr1- PHP_VERSION=8.4 BRANCH=v5 VARIANT=<variant> ./tests-suite/bash_unit -f tap ./tests-suite/*.sh

PHP	cli	apache	fpm
8.2	28/28	35/35	31/31
8.3	28/28	35/35	31/31
8.4	28/28	35/35	31/31
8.5	28/28	35/35	31/31

(amd64 locally, arm64 by the CI)

Checklist

• I followed the guidelines in CONTRIBUTING guide
• I have squashed any insignificant commits
• This change has comments for package types, values, functions, and non-obvious lines of code