Summary:
The test utility method CDCSDKYsqlTest::CheckTabletsInCDCStateTable() tries to get all the
state table entries with non-max checkpoint and compare their equality with the expected set of
entries. However when this method tries to filter out max checkpoint entries it incorrectly handles
the optional checkpoint field in state table row entry. Because of this the filtering logic does not
work and leads to test flakiness.

This diff fixes the incorrect handling of the optional field.
Jira: DB-14258

Test Plan: Jenkins: test regex: .*CDC.*

Reviewers: skumar, siddharth.shah

Reviewed By: siddharth.shah

Subscribers: ycdcxcluster

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D40311