🐛 BUG: Uncaught error when initializing two top level WASM modules

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

Miniflare

### What version(s) of the tool(s) are you using?

3.20231218.0

### What version of Node are you using?

v20.10.0

### What operating system are you using?

Mac

### Describe the Bug

When using dynamic imports to load two wasm modules in parallel using top-level await, any second `await` attempt failed with an uncaught error.

Minimal Reproduction: https://github.com/pi0/miniflare-reproduction

`mode-a.mjs` and `mode-b.mjs`:

```js
const mod = (await import("./sum.wasm")).default;
const instance = await WebAssembly.instantiate(mod);

export const sum = instance.exports.sum;
```

`worker.mjs`:

```js
let [a, b] = ["-", "-"];

// Only works if one await happens!
a = await import("./mod-a.mjs").then((r) => r.sum(1, 2));
b = await import("./mod-b.mjs").then((r) => r.sum(3, 4));

export default {
async fetch(request, env, ctx) {
// This works (also in parallel)
// a = await import("./mod-a.mjs").then((r) => r.sum(1, 2));
// b = await import("./mod-b.mjs").then((r) => r.sum(3, 4));

return new Response(JSON.stringify([a, b], null, 2), {
headers: { "content-type": "application/json" },
});
},
};
```

**Note:** Importing alone works, but any attempt to access or call exports fails with error:

**Stack trace:** (attached)

(minfilare config uses `modules: true` + `moduleRules` for `CompiledWasm`)

---

Context: Discovered in tests while working on https://github.com/unjs/unwasm/pull/11/ (unwasm will be used as the default WASM handler for Nuxt and Nitro projects and also for CF deployments 🔥 )
the

### Please provide a link to a minimal reproduction

https://github.com/pi0/miniflare-reproduction

### Please provide any relevant error logs

```
workerd/jsg/modules.c++:336: error: Async module was not immediately resolved.
service core:user:: Uncaught ReferenceError: Cannot access 'sum' before initialization
at src/worker.mjs:5:47
/Users/pooya/tmp/miniflare-reproduction/node_modules/miniflare/dist/src/index.js:8890
throw new MiniflareCoreError(
^

MiniflareCoreError [ERR_RUNTIME_FAILURE]: The Workers runtime failed to start. There is likely additional logging output above.
at #assembleAndUpdateConfig (/Users/pooya/tmp/miniflare-reproduction/node_modules/miniflare/dist/src/index.js:8890:13)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async Mutex.runWith (/Users/pooya/tmp/miniflare-reproduction/node_modules/miniflare/dist/src/index.js:3861:16)
at async #waitForReady (/Users/pooya/tmp/miniflare-reproduction/node_modules/miniflare/dist/src/index.js:8940:5)
at async Miniflare.dispatchFetch (/Users/pooya/tmp/miniflare-reproduction/node_modules/miniflare/dist/src/index.js:9004:5)
`````