control chunk size to optimize query latency and resource consumption

[zz-jason]

Currently we use 1024 as the default batch size, but some OLTP workloads may not need to read or return very much rows, thus we need a small batch size to reduce the overhead of making a big slice of size 1024

[zz-jason]

After this PR #8994, we are able to set required chunk size for each executor.