fix bug in expel replicaset

Summary

• fix: replicaset expel didn't work when master changed target state

Close #1114 (closed)

• test: cleanup: use Cluster.wait_has_states for checking instance state

• test: cleanup expelling in tests

• test: cleanup stuff related to figuring out leader and expelled instances

Instance info is cluster-wide information. You never need to call .instance_info on every single instance, they all have the same information. You only need to connect to a single instance to get all the info about the cluster (except for some runtime information, which is the rare case).

• test: cleanup some deprecated lua code

• test: cleanup naming in test_join_replicaset_after_expel

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• Cherry-pick to: none
• Docs follow-up: not necessary
• Changelog is updated