🐛 BUG: miniflare.dispatchFetch() buffers streaming responses

### Which Cloudflare product(s) does this pertain to?

Miniflare

### What versions are you using?

3.20241230.0[miniflare]

### What operating system and version are you using?

OSX 15.2

### Please provide a link to a minimal reproduction

_No response_

### Describe the Bug

I'm using miniflare in test to assert my app is delivering the expected chunks in a streamed response. When I run the miniflare server locally and hit the endpoint using `curl` I get the expected chunks delivered as soon as they are enqueued. When I use `miniflare.dispatchFetch()` the chunks are all delivered at once when the stream is closed, suggesting that `.dispatchFetch` is somehow buffering the response internally?

## Worker server code:

```ts
export const routeHandler = (request, env) => {
const stream = new ReadableStream({
async start(controller) {
const encoder = new TextEncoder();
let i = 0;

while (i++ < 3) {
controller.enqueue(encoder.encode(`${i}\n`));
console.log('enqueue', i);
await wait(1000);
}

controller.close();
}
});

const response = new Response(stream, {
headers: {
'content-type': 'text/plain',
'transfer-encoding': 'chunked',
},
});

return response;
};
```

## Client code

```ts
const res = await miniflare.dispatchFetch(
new URL('/cache/url/stream', 'http://localhost:4000/').toString(),
{
method: 'GET',
}
);

if (!res.body || !(res.body instanceof ReadableStream)) {
throw new Error('expected stream');
}

console.log('got status', res.status);

const reader = res.body.getReader();
const decoder = new TextDecoder();

while (true) {
const { value, done } = await reader.read();
console.log(decoder.decode(value));

if (done) {
break;
}
}
```

## Log output

```bash
[mf:inf] Ready on http://127.0.0.1:4000
enqueue 1
got status 200
[mf:inf] GET /cache/url/stream 200 OK (13ms)
enqueue 2
enqueue 3
1
2
3
```

Note how the client logs all happen after the final chunk is enqueued and the stream is closed.

### Please provide any relevant error logs

_No response_