Supports BatchListener

**FEATURE REQUEST**

1. Please describe the feature you are requesting.

Sometimes we need to analysis our batch messages, such as merge, filter duplicate contents.
Batch Listener May Helpful.
BatchMessageListener support each thread to be allocated n messages.

2. Provide any additional detail on your proposed use case for this feature.

In my consumer , I need to merge one batch messages, thus it can invoke rpc less.
Another case , consumer thread has been pushed 10 mesaages, and they have deplicate content , I want to filter and drop some.


3. Indicate the importance of this issue to you (blocker, must-have, should-have, nice-to-have). Are you currently using any workarounds to address this issue?

I've tried.