Fixup gentest-validate when directories have folders

Summary: This reworks `gentest-validate`, to be more resilient to changes like D58307002, which cause [validation failures](https://github.com/facebook/yoga/actions/runs/9653979292/job/26627690870) due to the file traversal code not handling the presence of directories.

Differential Revision: D58987293

package.json

@@ -23,5 +23,8 @@
     "eslint-plugin-prettier": "^4.2.1",
     "prettier": "2.8.8",
     "typescript": "5.0.4"
+  },
+  "resolutions": {
+    "cliui/wrap-ansi": "7.0.0"
   }
 }