public List<Region> getRegions() {
        return regions;
    }
A physical node in the cluster, embedded in an app java process,
store corresponds to a local file based rocksDB, a store contains
multiple regions, all regions share a rocksDB.

@author jiachun.fjc
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/metadata/Store.java