[Enhancement] PPL Alerting: Get Alerts V2 API response does not include start or end index for pagination

**Is your feature request related to a problem?**
Get Alerts V2 supports pagination, but does not give user all useful information for pagination, such as the last start index and the end index of the current response.

**What solution would you like?**
Get Alerts response should include the start and end indices so users can use them for reading in alerts by page.