Destroy HTTP cache connections on timeout

Summary:
Changelog: **[Fix]**: Destroy HTTP cache connections on timeout instead of hanging.

From Node's [docs](https://nodejs.org/api/http.html#event-timeout):

> [The `'timeout'` event is emitted] when the underlying socket times out from inactivity. This only notifies that the socket has been idle. The request must be destroyed manually.

Reviewed By: robhogan

Differential Revision: D51978782

fbshipit-source-id: 60bba1d35283853c9d3e27133c77045562f7148d

packages/metro-cache/src/stores/HttpStore.js

@@ -153,6 +153,10 @@ class HttpStore<T> {
         reject(new NetworkError(err.message, err.code));
       });
 
+      req.on('timeout', () => {
+        req.destroy(new Error('Request timed out'));
+      });
+
       req.end();
     });
   }
@@ -195,6 +199,10 @@ class HttpStore<T> {
         res.resume();
       });
 
+      req.on('timeout', () => {
+        req.destroy(new Error('Request timed out'));
+      });
+
       gzip.pipe(req);
 
       if (value instanceof Buffer) {