Summary:
Our deprecated approach was to implement vector index ourselves using RocksDB to store index related data.
We switched to another approach, with implementing vector index using existing libraries.
So existing partial implementation should be removed.
Jira: DB-13968

Test Plan: Jenkins

Reviewers: arybochkin, aleksandr.ponomarenko, slingam

Reviewed By: slingam

Subscribers: ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D39853