Missing Terms Aggregation Performance Optimization

[sandeshkr419]

https://opensearch.org/docs/latest/aggregations/bucket/missing/

This is a follow-up on single bucket Terms Aggregation optimization: #11643 to ensure that the optimization works or not for Rare Terms Aggregation. If not, then we need to make required changes to make sure that this case is covered for the optimized code flow.

Next steps:

• Debug code to check existing flow
• If optimized, do nothing. If not, make changes to include this case.

[ajleong623]

I am interested in working on this.

[sandeshkr419]

Thanks @ajleong623 to help here. Let me know if you need any help once you start digging into it.