Improve progress-reporting in TezProcessor

Another one on behalf of Selina Zhang and Chris Drome. Following the example in Apache Tez's MapProcessor, TezProcessor ought to use ProgressHelper to report progress for a Tez task. As per Kuhu Shukla's advice,

Tez... provides getProgress() API for AbstractLogicalInput(s) which will give the correct progress value for a given Input. The TezProcessor(s) in Hive should use this to do something similar to what MapProcessor in Tez does today, which is use/override ProgressHelper to get the input progress and then set the progress on the processorContext.
...
The default behavior of the ProgressHelper class sets the processor progress to be the average of progress values from all inputs.

This code is whacked from inspired by MapProcessor's use of ProgressHelper.

(For my reference, YHIVE-978.)