optimize StreamUtil and fix the LimitingExecutor

[xiaoyu-yang-gh]

(1) #548 fixed the issue to execute mapper function to each batch in the thread-pool. but the batches are still executed sequentially. We need to fix the issues to have the batches executed in parallel. Here we implement a Collector:
- the accumulate method collect data from original stream, create batches, and submit jobs for executing each batch to thread-pool.
- the finisher method handles the last batch, submit the job for the last batch to thread-pool. It also connect the result for the jobs executed in the thread-pool, combine the results, and stream the results.

Tested this can execute the batches in the thread-pool in parallel.

(2) Fix LimitingExecutor. LimitingExecutor use a Semaphore to control the maximum number of jobs concurrently executed in the thread-pool. But the Semaphore is just used to guard the ThreadPool.execute(command), and the ThreadPool.execute just submit the job to the threadpool. So the Semaphore does not guard the number of jobs concurrently running in the pool. We fix this issue by:
a. require a Semaphore when submitting a new job;
b. release a Semaphore when a job completes;

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (9f838a0) 46.19% compared to head (61aa961) 46.29%.

Files	Patch %	Lines
...om/linkedin/avroutil1/builder/util/StreamUtil.java	83.33%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #550      +/-   ##
============================================
+ Coverage     46.19%   46.29%   +0.09%     
- Complexity     4548     4550       +2     
============================================
  Files           407      407              
  Lines         28443    28455      +12     
  Branches       4642     4643       +1     
============================================
+ Hits          13140    13172      +32     
+ Misses        13731    13715      -16     
+ Partials       1572     1568       -4     

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[xiaoyu-yang-gh]

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