Fix the setup for duplicate block local-cluster tests

[AshwinSekar]

Problem

After

• test_duplicate_shreds_switch_failure() is flaky, fixup and reenable.
• test_duplicate_shreds_broadcast_leader() does not test the case where duplicate proofs are disseminated through gossip, add 1 epoch delay to ensure gossip: notify state machine of duplicate proofs #32963 (comment) is tested
• rework the setup for test_duplicate_shreds_broadcast_leader_ancestor_hashes(), so that it can be enabled. Currently the setup does not allow for a successful ancestor hashes response.