default CompletableFuture<List<Boolean>> existsAll(List<Get> gets) {
    return allOf(exists(gets));
  }
A simple version for batch exists. It will fail if there are any failures and you will get the
whole result boolean list at once if the operation is succeeded.
@param gets the Gets
@return A {@link CompletableFuture} that wrapper the result boolean list.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncTable.java