feature(cluster_aws): read user_data_format_version from AMI tags
feature(cluster_aws): read user_data_format_version from AMI tags

renaming the old `sci_version` tag to `user_data_format_version`

Ref: scylladb/scylla-machine-image#21

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests