[FEATURE] Improve adaptive rate limit to handle lower rate

[ykmr1224]

Is your feature request related to a problem?
Currently, bulk request uses fixed batch size.
When we set lower min rate for adaptive rate limit and the rate goes down, the frequency of the request goes down and that causes rate increase to be very slow. (If the batch size is 5000, and rate goes down to 500 req/sec, the actual request is sent every 10 sec, and additive increase happen only 1 time per 10 sec)

Lower rate is required for higher number of executor nodes.

What solution would you like?
Adjust the batch size based on the rate to send request more constantly and adjust the rate as well.