Feature request: To be able to set `custom audience` in V2 functions

### Related issues

Couldn't find any.

### [REQUIRED] Version info

**node:** v18.16.0

**firebase-functions:** 4.4.0

**firebase-tools:** 12.0.0

**firebase-admin:** 11.8.0

### Feature request

I am using a load balancer on top of firebase functions to direct traffics to necessary API endpoints on a single domain. However, Cloud Run's custom authentication returns 401 if I set the `aud` field in the token as my custom domain because the `custom audience` needs to be set as per the documentation here: https://cloud.google.com/run/docs/configuring/custom-audiences

Since there is no option to set custom audience in `HttpsOptions`, I have to manually run
`gcloud beta run services update --add-custom-audiences=https://custom.endpoint.com` to add custom audiences.

It would be nicer to be able to set this when we are making firebase function itself, like:
```typescript
functionsV2.https.onRequest(
{
memory: "1GiB",
ingressSettings: "ALLOW_INTERNAL_AND_GCLB",
invoker: "private",
customAudiences: ["https://custom.endpoint.com"]
},
connectApp,
)
```

It seems like it's supported on terraform (https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/cloud_run_service#annotations) in the form of `annotations` so it might be nicer to support annotations when making firebase functions V2.