Open handles detected in Jest when using MockAgent

Bug Description

When testing using MockAgent in Jest, open handles are detected.

Reproducible By

I have created a minimal reproduction repository here: undici-open-handles. The README will provide all the guidance you need to reproduce the issue.

Expected Behavior

Having made a request using the MockAgent, and closed the MockAgent, no handles should be left open.

Logs & Screenshots

If you run the reproduction repository, you'll have the full logs, but here is a sample:

       9 |   client.intercept({ path: '/foo' }).reply(200, 'mockResponse')
      10 |
    > 11 |   const result = await request('http://test.com/foo').then((x) => x.body.text())
         |                               ^
      12 |
      13 |   expect(result).toBe('mockResponse')
      14 |

      at new RequestHandler (node_modules/undici/lib/api/api-request.js:38:7)
      at MockAgent.request (node_modules/undici/lib/api/api-request.js:193:25)
      at node_modules/undici/lib/api/api-request.js:186:15
      at MockAgent.request (node_modules/undici/lib/api/api-request.js:185:12)
      at node_modules/undici/index.js:76:15
      at repro.spec.ts:11:31
      at repro.spec.ts:8:71
      at Object.<anonymous>.__awaiter (repro.spec.ts:4:12)
      at Object.<anonymous> (repro.spec.ts:3:51)

Environment

Additional context

I attempted to investigate the implementation of MockAgent, and dig into the stack trace provided by Jest's detectOpenHandles. The issue seems to be to do with the AsyncResource extended by RequestHandler not getting cleaned up correctly. But I am not familiar with how AsyncResource should be used and I can't immediately see what the issue is.

Start with the README and repro.spec.ts in the linked undici-open-handles repository, then trace MockAgent and RequestHandler through lib/api/api-request.js. Investigate how the AsyncResource lifecycle is handled after a request and MockAgent.close(). Done means the reproduction completes without Jest detecting open handles.