Search and reindex fixes

[l-trotta]

Some validation fixes, mainly missing aggregations.

Reindex

• Field _source should be the same type as in SearchRequest, so a SearchConfig. server code

Search

• Missing cartesian_bounds aggregation: Request, Response
• Missing cartesian_centroid aggregation: Request, Response
• Missing change_point aggregation: Request, Response

These should all be safe to backport.

[github-actions]

Following you can find the validation changes against the target branch for the APIs.

API	Status	Request	Response
reindex	🔴 → 🟢	20/21 → 21/21	20/20
search	🔴	2551/2608 → 2569/2608	2608/2608

You can validate these APIs yourself by using the make validate target.

[l-trotta]

splitting in 2 for backporting reasons