Allow arbitrary Scylla versions in CcmBridge (#417) #850

Job	Run time
Setup ITs	6s
Unit tests (8)	2m 1s
Build (8)	59s
Full verify (8)	1m 42s
Cassandra ITs (RELEASE-3.X, 8)	19m 35s
Scylla ITs (ENTERPRISE-RELEASE, 8)	10m 27s
Cassandra ITs (RELEASE-4.X, 8)	22m 3s
Scylla ITs (ENTERPRISE-PRIOR-RELEASE, 8)	29m 19s
Scylla ITs (OSS-RELEASE, 8)	10m 55s
Scylla ITs (OSS-PRIOR-RELEASE, 8)	10m 33s
	1h 47m 40s

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