Summary:
The user could drop vector index.
Need to provide appropriate actions in tserver/master side for this scenario.
Jira: DB-15712

Test Plan: PgVectorIndexTest.Drop/*

Reviewers: arybochkin, zdrudi

Reviewed By: arybochkin, zdrudi

Subscribers: mhaddad, ybase, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D42481