Support get N or all messages from channel in one command

[longquanzheng]

• OneToAll
• ZeroToAll
• N (constant number)

this will be good for optimization.

Today for receiving N messages in a command is already working, but in a non-ideal way. Because workflow will have to repeat the command N times in a commandRequest. In the implementation, it will wait for each command separately. If N=2, then this mean that the state could consume 1 message, and then waiting for another one.

Partially consume and wait could cause potential "deadlock" situation. Ideally, it should wait and consume N messages atomically -- if they are all ready then consume, otherwise do not consume.

[longquanzheng]

Make sure to call drain signals before waiting

[longquanzheng]

duplicate of #280