Add PHPStan configuration for Symfony4 tests

- Created a new phpstan.neon file in the Symfony4 tests directory.
- Configured paths and excluded Symfony3 directory.
- Added bootstrap files for autoloading.
- Set dynamic constant names and adjusted reporting settings.
- Established PHPStan level to 6 for stricter analysis.

.vscode/ftp-kr.sync.cache.json

@@ -117,7 +117,7 @@
     },
     "google-merchant_id-1.xml": {
       "type": "-",
-      "size": 18590189,
+      "size": 18328944,
       "lmtime": 0,
       "modified": true
     },
@@ -194,6 +194,12 @@
       "modified": false
     },
     "img": {},
+    "import-products.php": {
+      "type": "-",
+      "size": 13877,
+      "lmtime": 0,
+      "modified": false
+    },
     "index.php": {
       "type": "-",
       "size": 1169,
@@ -273,6 +279,12 @@
       "lmtime": 0,
       "modified": false
     },
+    "sollux_import_log.csv": {
+      "type": "-",
+      "size": 19,
+      "lmtime": 0,
+      "modified": false
+    },
     "src": {},
     "stany_elmar": {},
     "themes": {},