Summary:
Currently we create vector index only when it was initially added to the tablet.
So any vector index data is not used after restart.
This diff adds logic to create vector index on tablet bootstrap.
So we could use vector index data stored before restart.

Important note:
Correct operation replay is not implemented yet.
So non flushed data could be missing in vector index.
Jira: DB-14460

Test Plan: PgVectorIndexTest.Restart/*

Reviewers: arybochkin, aleksandr.ponomarenko

Reviewed By: arybochkin

Subscribers: ybase, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D40571