Update to Symfony 7 (#204)

Update to Symfony 7 and update all dependencies #201.

Unrelated changes:
* Remove unused imports.
* Shutdown gracefully when hotreload is used.

bin/restartOnChange

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-trap 'kill $(jobs -p)' EXIT
+trap 'kill $(jobs -p) && wait' EXIT
 
 while true; do
   $@ &

composer.json

@@ -19,7 +19,7 @@
     }
   },
   "require": {
-    "php": "^8.2",
+    "php": "^8.3",
     "ext-pcntl": "*",
     "ext-posix": "*",
     "ext-session": "*",
@@ -38,24 +38,24 @@
     "psr/clock": "^1.0",
     "psr/event-dispatcher": "^1.0",
     "psr/log": "^3.0",
-    "symfony/asset": "^6.3",
-    "symfony/asset-mapper": "^6.3",
-    "symfony/clock": "^6.2",
-    "symfony/config": "^6.3",
-    "symfony/console": "^6.3",
-    "symfony/finder": "^6.3",
-    "symfony/framework-bundle": "^6.3",
-    "symfony/http-client": "^6.3",
-    "symfony/http-foundation": "^6.3",
-    "symfony/http-kernel": "^6.3",
-    "symfony/lock": "^6.2",
+    "symfony/asset": "^7.0",
+    "symfony/asset-mapper": "^7.0",
+    "symfony/clock": "^7.0",
+    "symfony/config": "^7.0",
+    "symfony/console": "^7.0",
+    "symfony/finder": "^7.0",
+    "symfony/framework-bundle": "^7.0",
+    "symfony/http-client": "^7.0",
+    "symfony/http-foundation": "^7.0",
+    "symfony/http-kernel": "^7.0",
+    "symfony/lock": "^7.0",
     "symfony/monolog-bundle": "^3.8",
-    "symfony/security-bundle": "^6.3",
+    "symfony/security-bundle": "^7.0",
     "symfony/service-contracts": "^3.3",
-    "symfony/twig-bundle": "^6.3",
-    "symfony/uid": "^6.3",
-    "symfony/validator": "^6.3",
-    "symfony/yaml": "^6.3",
+    "symfony/twig-bundle": "^7.0",
+    "symfony/uid": "^7.0",
+    "symfony/validator": "^7.0",
+    "symfony/yaml": "^7.0",
     "twig/twig": "^3.4"
   },
   "require-dev": {
@@ -68,10 +68,10 @@
     "phpunit/phpunit": "^10.3",
     "roave/security-advisories": "dev-master",
     "squizlabs/php_codesniffer": "^3.7",
-    "symfony/debug-bundle": "^6.3",
-    "symfony/error-handler": "^6.3",
-    "symfony/stopwatch": "^6.3",
-    "symfony/web-profiler-bundle": "^6.3"
+    "symfony/debug-bundle": "^7.0",
+    "symfony/error-handler": "^7.0",
+    "symfony/stopwatch": "^7.0",
+    "symfony/web-profiler-bundle": "^7.0"
   },
   "config": {
     "sort-packages": true,