Make the php command 2 times faster to start - #426

Summary

This PR makes the php command 2 times faster to start:

• Bug
• Feature
• Breaking changes

/usr/bin/php is a proxy that regenerates the PHP configuration when a PHP_* variable changed (e.g.
docker exec -e PHP_INI_MEMORY_LIMIT=1G). To detect it, it called sudo and started PHP a first time on each call.
It now compares a fingerprint of the PHP_* variables in bash, and only uses sudo and PHP when they changed.

It also detects the removed variables: the configuration was kept unchanged when a PHP_* variable was removed.

Measures (PHP 8.4, amd64, average of 300 php -r '' in a started container):

Every php command benefits: Composer scripts, bin/console, cron jobs, tests...

Test plan (required)

New test test_environmentChangedAfterStart (php-ini.sh). It fails on the current images
(expected [512M -1] but was [512M 512M]).

TAG_PREFIX=pr-perf- docker buildx bake --load php8X-slim-<variant> php8X-<variant>
TAG_PREFIX=pr-perf- PHP_VERSION=8.X BRANCH=v5 VARIANT=<variant> ./tests-suite/bash_unit -f tap ./tests-suite/*.sh

variant-node.sh was not run: the NodeJS images are not modified.

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