Add possibility to execute batch queries using rows of a single partition

[vponomaryov]

As of now, if we use large partitions and want to populate data using batches then
We will get balanced approach for partitions of a partition group.
It will cause batch queries have rows for different partitions as much as possible.
Such an approach is useful for read queries, not write ones.

So, need to add possibility to perform write batches sequentially where one batch would contain rows targeted only at some one partition.