Unify the config formats for cluster.core_nodes and cluster.statics.seeds. Now they both support formats in array ["emqx1@127.0.0.1", "emqx2@127.0.0.1"] or semicolon-separated string "emqx1@127.0.0.1,emqx2@127.0.0.1".
cluster.core_nodes
cluster.statics.seeds
["emqx1@127.0.0.1", "emqx2@127.0.0.1"]
"emqx1@127.0.0.1,emqx2@127.0.0.1"