Emulator dashboard timeout when accessing exported data

### [REQUIRED] Environment info

Tools v11.1.0
**firebase-tools:**

**Platform: MacOS**

### [REQUIRED] Test case

Loading any kind of production seed makes the emulator UI timeout.

### [REQUIRED] Steps to reproduce

Load an export from Firestore, at around 50mb is enough o make the UI not work.

### [REQUIRED] Expected behavior

Be able to access all documents via the emulator UI

### [REQUIRED] Actual behavior

Emulator loads, the data is there as our apps can access it normally via their SDK, but the emulator UI can't.

https://user-images.githubusercontent.com/29472480/174684112-53fea825-a0db-4df3-8c74-7553f456e46c.mov

[firebase-debug.log](https://github.com/firebase/firebase-tools/files/8943963/firebase-debug.log)
[firestore-debug.log](https://github.com/firebase/firebase-tools/files/8943969/firestore-debug.log)

Start by reproducing the timeout in the emulator dashboard with a roughly 50 MB Firestore export. Read firestore-debug.log and firebase-debug.log while checking whether the emulator UI can load the exported documents. Done means the dashboard exposes all documents while applications continue to access the data normally through their SDKs.

Written by the indexing model from the issue text.