src: add test flag to config file

PR-URL: #60798
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

Author: marco-ippolito

doc/node-config-schema.json

@@ -833,6 +833,9 @@
           "type": "boolean",
           "description": "launch test runner on startup"
         },
+        "test": {
+          "type": "boolean"
+        },
         "test-concurrency": {
           "type": "number",
           "description": "specify test runner concurrency"