[Enhancement] (nereids)implement adminRebalanceDiskCommand in nereids

[LiBinfeng-01]

adminRebalanceDisk command is supported in legacy planner but not in nereids(new doris fe planner). you need implement the following adminRebalanceDisk command in nereids:
unsupportedadminRebalanceDiskStatement

        (COMMA backends+=STRING_LITERAL) RIGHT_PAREN)?                              ```