Re-implement DistinctCombineOperator to utilize more threads to merge

[Jackie-Jiang]

On top of #14701

The combine algorithm is as following:

Use an atomic reference as the swap space to merge the results blocks.

• If the swap space is null, put the new results block in it.
• If the swap space is not null, take the results block from the swap space, and merge it with the new results block.

Repeat this process until successfully put the new results block in the swap space.
After all threads are done, the results block in the swap space is the final merged results block.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 70.40720% with 625 lines in your changes missing coverage. Please review.

Project coverage is 63.82%. Comparing base (59551e4) to head (c4fe425).
Report is 1509 commits behind head on master.

Files with missing lines	Patch %	Lines
.../core/query/distinct/table/BytesDistinctTable.java	51.92%	48 Missing and 27 partials ⚠️
...t/core/query/distinct/table/LongDistinctTable.java	59.25%	47 Missing and 19 partials ⚠️
.../query/distinct/table/BigDecimalDistinctTable.java	62.82%	32 Missing and 26 partials ⚠️
...core/query/distinct/table/StringDistinctTable.java	62.82%	40 Missing and 18 partials ⚠️
...perator/query/DictionaryBasedDistinctOperator.java	76.47%	35 Missing and 9 partials ⚠️
...y/distinct/raw/RawMultiColumnDistinctExecutor.java	49.41%	34 Missing and 9 partials ⚠️
.../core/query/distinct/table/FloatDistinctTable.java	72.07%	23 Missing and 20 partials ⚠️
...core/query/distinct/table/DoubleDistinctTable.java	75.48%	22 Missing and 16 partials ⚠️
...ot/core/query/distinct/table/IntDistinctTable.java	77.16%	19 Missing and 18 partials ⚠️
...y/DictionaryBasedSingleColumnDistinctExecutor.java	73.75%	15 Missing and 6 partials ⚠️
... and 18 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #14714      +/-   ##
============================================
+ Coverage     61.75%   63.82%   +2.07%     
- Complexity      207     1607    +1400     
============================================
  Files          2436     2702     +266     
  Lines        133233   150647   +17414     
  Branches      20636    23272    +2636     
============================================
+ Hits          82274    96147   +13873     
- Misses        44911    47314    +2403     
- Partials       6048     7186    +1138     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (+99.99%)	⬆️
integration	100.00% <ø> (+99.99%)	⬆️
integration1	100.00% <ø> (+99.99%)	⬆️
integration2	0.00% <ø> (ø)
java-11	63.80% <70.40%> (+2.09%)	⬆️
java-21	63.70% <70.40%> (+2.08%)	⬆️
skip-bytebuffers-false	63.81% <70.40%> (+2.07%)	⬆️
skip-bytebuffers-true	63.69% <70.40%> (+35.96%)	⬆️
temurin	63.82% <70.40%> (+2.07%)	⬆️
unittests	63.81% <70.40%> (+2.07%)	⬆️
unittests1	56.25% <70.40%> (+9.36%)	⬆️
unittests2	34.16% <0.00%> (+6.43%)	⬆️

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