Add an option to limit the concurrent compact

[cs-lpc]

What would you like to be added:

add an option to limit the concurrent compact

Why is this needed: In some use case, we need more threads to compact data. Especially when the data in local cache. But we can not change the number of threads by configuration

[cs-lpc]

We have faced this problem, and modified the number of compact concurrent. And found no problems in the test