Move utility functions to e2eutil

There's some utility functions that live in the test files they're made for, and we could do with moving them to e2eutil instead;

• S3 functions in backup_test.go
• LDAP setup in ldap_test.go
• Enabling monitoring at the top of monitoring_test.go (although it's probably worth replacing this with .WithMonitoring() in the cluster options)
• PVC setup and verification in persistentvolume_test.go
• RBAC setup in rbac_test.go
• RZA utility functions in rza_test.go
• cbopinfo functions and such in supportability_test.go
• Upgrade event sequences in upgrade_test.go  ?
• Lots of support code in validation_test.go
• XDCR helper functions in xdcr_test.go