Change the test files that add/remove coordinator as a node.

This issue is to track the remaining work in #6847.

#6847 makes sure that we add the coordinator to metadata when creating clusters for our test runs. Ideally we would like to check at the end of a schedule, if the coordinator is in metadata in a file like this:

**check_post_schedule_state.sql**
` SELECT count(*) > 1 as coordinator_exists FROM pg_dist_node WHERE groupid = 0 AND isactive
`

However, some tests add/remove coordinator as a node multiple times as part of their test scenarios. It should be possible to change those tests in the following ways:

- they use an additional worker node such as worker_3_node instead.
- they change the coordinator properties to have shards/not to have shards to use it as a node instead of adding/removing it.