[NET-7658] Restore service endpoints ID to target, use sibling field for storing route port

[nathancoleman]

Description

https://github.com/hashicorp/consul/pull/20400 replaced the ServiceEndpointsId field w/ a full EndpointRef; however, @rboyer pointed out that this doesn't match the direction we want to go in long term. Instead, this PR adds a sibling field for the route port and restores the ID that was previously there.

Testing & Reproduction steps

Links

PR Checklist

• [x] updated test coverage
• [ ] external facing docs updated
• [x] appropriate backport labels added
• [x] not a security concern

[github-actions[bot]]

This pull request has been automatically flagged for inactivity because it has not been acted upon in the last 60 days. It will be closed if no new activity occurs in the next 30 days. Please feel free to re-open to resurrect the change if you feel this has happened by mistake. Thank you for your contributions.

[github-actions[bot]]

Closing due to inactivity. If you feel this was a mistake or you wish to re-open at any time in the future, please leave a comment and it will be re-surfaced for the maintainers to review.