Summary:
The test for #25917 used a query against catalog tables, the same query
as in the bug report. However, the content of the catalog tables is not
stable, in particular, the landed diff D44291 took test failure rate to 100%.

This diff creates and populates custom tables to query instead of
catalog tables. The query plan has the same shape and tests the same
feature as the previous.

The test query fixed here is probably not the only source of the test
instability, since the test was muted before D44291 has landed. We
should keep an eye on the test stability and make follow up fix if still
unstable.
Jira: DB-15715

Test Plan: ./yb_build.sh --java-test org.yb.pgsql.TestPgRegressJoin#testPgRegressJoin

Reviewers: aagrawal, mtakahara

Reviewed By: mtakahara

Subscribers: yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D44775