refactor: Add a few lint rules to test files in /spec (#9815)

spec/eslint.config.js

@@ -48,10 +48,20 @@ module.exports = [
       },
     },
     rules: {
-      "no-console": "off",
-      "no-var": "error",
-      "no-unused-vars": "off",
+      indent: ["error", 2, { SwitchCase: 1 }],
+      "linebreak-style": ["error", "unix"],
+      "no-trailing-spaces": "error",
+      "eol-last": "error",
+      "space-in-parens": ["error", "never"],
+      "no-multiple-empty-lines": "warn",
+      "prefer-const": "error",
+      "space-infix-ops": "error",
       "no-useless-escape": "off",
-    }
+      "require-atomic-updates": "off",
+      "object-curly-spacing": ["error", "always"],
+      curly: ["error", "all"],
+      "block-spacing": ["error", "always"],
+      "no-unused-vars": "off",
+    },
   },
 ];