Implement ArrayMergeBuilder

[Tigrov]

Related PR

• Add functions as expressions db#1029

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌
Fixed issues

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.77%. Comparing base (af7864f) to head (ec73a26).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #439   +/-   ##
=========================================
  Coverage     99.77%   99.77%           
- Complexity      298      304    +6     
=========================================
  Files            33       34    +1     
  Lines           884      898   +14     
=========================================
+ Hits            882      896   +14     
  Misses            2        2           

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