Create pubsub function with dead letter

Hello,

Not really a bug, it is more an improvement.

I search a way to configure a dead letter topic to the subscription that is automatically created when I deploy a new pubsub cloud function.
Actually my workaround is to configure the dead letter after cloud function creation.

I saw this [issue](https://github.com/firebase/firebase-functions/issues/836) but there is not a fix.

### [REQUIRED] Version info

**node:**
16.16.0

**firebase-functions:**
4.1.0

**firebase-tools:**
10.2.0

**firebase-admin:**
11.0.1

### [REQUIRED] Test case
Implement a pubsub cloud function with firebase-functions.
Deploy it with firebase cli.
There is no way to define a dead letter.

### [REQUIRED] Steps to reproduce
Implement a cloud function with a pubsub trigger
`functions
.region('europe-west3')
.runWith()
.pubsub.topic('SignalEvent')
.onPublish(...)`

----> No option to configure a dead letter

### [REQUIRED] Expected behavior
I want to configure dead letter parameters with a specific option.

### [REQUIRED] Actual behavior
We can't configure dead letter topic and other dead letter parameters.

No source file or test is named. Start by tracing how the Firebase CLI deploys the subscription automatically created for a Pub/Sub cloud function, using the .pubsub.topic('SignalEvent') entry point described here. Done means a specific option configures the dead-letter topic and related parameters during deployment, with coverage for the deployment behavior.

Written by the indexing model from the issue text.