Summary:
The function `pg_copy_logical_replication_slot()` was introduced in YB code with the PG 15 merge. This function can be used to create a copy of an existing logical replication slot. However, we don't support copying of replication slots / CDC streams yet in YB. This diff adds guardrails which will cause  `pg_copy_logical_replication_slot()` to fail with correct error message.
Jira: DB-14334

Test Plan: Manual testing

Reviewers: vkushwaha, skumar

Reviewed By: vkushwaha

Subscribers: vkushwaha, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D42297