Some bugs with BATCH operations after enabling, /ru-prestable

[dahbka-lis]

1. Counter BatchOperations/Delete/Bytes is always zero. We decided to remove bytes counters because we cannot get the bytes of all deleted/updates rows, only their size of PKs.
2. Logs are unclear and do not provide any information. Need to improve.
3. Some errors can return without any message of errors (UNAVAILABLE for max retry cnt).