[New] core: fs/promises is a core module again in node 14+

Author: ljharb

lib/core.json

@@ -16,7 +16,7 @@
     "events": true,
     "freelist": "< 6",
     "fs": true,
-    "fs/promises": ">= 10 && < 10.1",
+    "fs/promises": [">= 10 && < 10.1", ">= 14"],
     "_http_agent": ">= 0.11.1",
     "_http_client": ">= 0.11.1",
     "_http_common": ">= 0.11.1",