raft_client: calculate batch size more approximately (#7522)
raft_client: calculate batch size more approximately (#7522)

Signed-off-by: qupeng <61d746964f2cf9aa900605464d8422efaad5ea7d@pingcap.com>
c4pt0r/tikv,BusyJay/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv