AWS::OpenSearchService::Domain - CNAME of CustomDomain should reference Domain endpoint v2 (dual stack)

### Name of the resource

AWS::OpenSearchService::Domain

### Resource name

_No response_

### Description

Currently the AAAA DNS-CNAME-Entry for the Custom Domain Name references the
**Domain endpoint (IPv4)**: NAME.REGION.es.amazonaws.com

That would be okay for the A Record, but the AAAA-Record should reference
**Domain endpoint v2 (dual stack)**: NAME.aos.REGION.on.aws
if this endpoint is available. if it's not available, an AAAA doesn't need to be created.

### Other Details

_No response_

Start by tracing AWS::OpenSearchService::Domain handling for CustomDomain and its AAAA DNS-CNAME entry. Verify when the Domain endpoint v2 (dual stack) is available and ensure the finished behavior uses it for the AAAA record or creates no AAAA record when it is unavailable.

Written by the indexing model from the issue text.