Set Amplify Auth triggers via override.ts

### Before opening, please confirm:

- [X] I have installed the latest version of the Amplify CLI (see above), and confirmed that the issue still persists.
- [X] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-cli/issues?q=is%3Aissue+).
- [X] I have read the guide for [submitting bug reports](https://github.com/aws-amplify/amplify-cli/blob/master/CONTRIBUTING.md#bug-reports).
- [X] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.

### How did you install the Amplify CLI?

_No response_

### If applicable, what version of Node.js are you using?

_No response_

### Amplify CLI Version

7.6.5

### What operating system are you using?

Mac

### Amplify Categories

auth

### Amplify Commands

push

### Describe the bug

Hello,

before the amplify cli auth upgrade and the introduction of the override.ts file, we configured our Lamba Config Parameters in the `parameters.json` file via
```json
"functionPostConfirmationArn": {
"Fn::GetAtt": ["functionPostConfirmation", "Outputs.Arn"]
}
```
But now this is not possible anymore and we are stuck doing deployments.

So now we need to implement the same in our override.ts file to be able to run deployments again.
```typescript
resources.userPool.lambdaConfig = {
...resources.userPool.lambdaConfig,
postConfirmation: {
"Fn::GetAtt": ["functionPostConfirmation", "Outputs.Arn"]
},
};
```

We are not using the cognito triggeres configured by amplify because of #9382 .

We are really having trouble at the moment and we would appreciate quick help.

Thank you

Kind regards
Hendrik

### Expected behavior

-

### Reproduction steps

-

### GraphQL schema(s)

```graphql
# Put schemas below this line

```

### Log output

```
# Put your logs below this line

```

### Additional information

_No response_

Start by reading the auth upgrade's override.ts handling and the previous parameters.json configuration, then review the related discussion in #9382. The work is complete when an auth user pool can receive the post-confirmation Lambda ARN through override.ts and deployments succeed with amplify push.

Written by the indexing model from the issue text.