Add `MockResolverIT#replace_cluster_test()` #668

Job	Run time
Unit tests (8)	2m 0s
Setup ITs	6s
Full verify (8)	1m 40s
Build (8)	56s
Cassandra ITs (RELEASE-3.X, 8)	20m 5s
Scylla ITs (ENTERPRISE-RELEASE, 8)	29m 43s
Cassandra ITs (RELEASE-4.X, 8)	22m 8s
Scylla ITs (ENTERPRISE-PRIOR-RELEASE, 8)	35m 50s
Scylla ITs (OSS-RELEASE, 8)	10m 7s
Scylla ITs (OSS-PRIOR-RELEASE, 8)	10m 26s
Scylla ITs (ENTERPRISE-RC, 8)	10m 2s
Scylla ITs (OSS-RC, 8)	10m 17s
	2h 33m 20s

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