phpstan: Streamline vendor file location with local dev-env

phpstan is not run with an action anymore, as the action runs
it its own docker container and hence has no access to files
outside the repository root. A side-effect of this is, that
phpstan now **really** runs with the php version set up by
the matrix.

.github/workflows/php.yml

@@ -32,8 +32,8 @@ jobs:
 
       - name: Setup dependencies
         run: |
-          composer require -n --no-progress overtrue/phplint
-          git clone --depth 1 https://github.com/Icinga/icingaweb2.git vendor/icingaweb2
+          composer require -n --no-progress overtrue/phplint phpstan/phpstan
+          sudo git clone --depth 1 https://github.com/Icinga/icingaweb2.git /icingaweb2
 
       - name: PHP Lint
         if: ${{ ! cancelled() }}
@@ -45,7 +45,7 @@ jobs:
 
       - name: PHPStan
         if: ${{ ! cancelled() }}
-        uses: php-actions/phpstan@v3
+        run: ./vendor/bin/phpstan analyse
 
   test:
     name: Unit tests with php ${{ matrix.php }} on ${{ matrix.os }}

phpstan.neon

@@ -12,7 +12,7 @@ parameters:
         - src
 
     scanDirectories:
-        - vendor
+        - /icingaweb2
 
     ignoreErrors:
         -