Add option for unlimited phoenix.query.QueueSize

As discussed in PHOENIX-7117  phoenix.query.queueSize limits can cause scan queries on table with lot of regions to fail. I did some profiling and found that each task allocates 48 bytes. So I am adding an enhancement to make the queue size unlimited if we set the limit to -1. We still have a limit on the number of tasks that can be executed in parallel controlled by the 
phoenix.query.threadPoolSize
 
If you don't enforce the limit, the only thing that is limiting is the jvm heap allocated.