Issue 951

[andyfengHKU]

This PR partially solves #951 to avoid flattening when multiple aggregate function presents.

The idea is that when evaluating an aggregate function, we input not only the aggregate vector but also other unFlat state to obtain a correct multiplicity.

E.g.

MATCH (a), (b) RETURN COUNT(a), COUNT(b);

During aggregating, COUNT(a) will take vector "a" and also the state of vector "b" to figure the actual count.

At implementation level, we use AggregateInput (which wraps aggregate vector and unFlat data chunks) to replace AggregateVector

[codecov]

Codecov Report

Patch coverage: 98.18% and project coverage change: +0.38 🎉

Comparison is base (7f9d84c) 91.87% compared to head (2f98f2c) 92.26%.

❗ Current head 2f98f2c differs from pull request most recent head f3b1f2a. Consider uploading reports for the commit f3b1f2a to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1508      +/-   ##
==========================================
+ Coverage   91.87%   92.26%   +0.38%     
==========================================
  Files         677      677              
  Lines       24396    24356      -40     
==========================================
+ Hits        22415    22472      +57     
+ Misses       1981     1884      -97     

Impacted Files	Coverage Δ
.../logical_plan/logical_operator/logical_aggregate.h	100.00% <ø> (ø)
src/include/processor/mapper/plan_mapper.h	100.00% <ø> (ø)
...rc/processor/operator/aggregate/base_aggregate.cpp	93.10% <95.00%> (-6.90%)	⬇️
src/processor/mapper/map_aggregate.cpp	98.43% <96.42%> (-1.57%)	⬇️
src/include/processor/data_pos.h	100.00% <100.00%> (ø)
...rocessor/operator/aggregate/aggregate_hash_table.h	77.77% <100.00%> (ø)
...ude/processor/operator/aggregate/aggregate_input.h	100.00% <100.00%> (ø)
...lude/processor/operator/aggregate/base_aggregate.h	75.00% <100.00%> (-5.00%)	⬇️
...processor/operator/aggregate/base_aggregate_scan.h	100.00% <100.00%> (ø)
...lude/processor/operator/aggregate/hash_aggregate.h	100.00% <100.00%> (ø)
... and 9 more

... and 59 files with indirect coverage changes

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