…avor of `logGroup`

See #28737 for full details.

Some custom resources have made the `logRetention` property part of their own API. In these cases, we are now also deprecating `logRetention`.

Migrating log groups for custom resource would follow the same steps as outline in #28737. Given that custom resource logging is for debugging purposes and there are no guarantees about the output format, it should be possible to simply replace `logRetention` with a simple `logGroup` in most cases:

```ts
const awsCustom1 = new cr.AwsCustomResource(this, 'API1', {
  // Replace this
  logRetention: logs.RetentionDays.ONE_WEEK,
  // with
  logGroup: new logs.LogGroup(this, 'AwsCustomResourceLogs', {
    retention: logs.RetentionDays.ONE_WEEK,
  }),
});
```