[Feature] Support coalesce literal

[61yao]

Add support for coalesce literal. We treat literal as non-null only.

[codecov-commenter]

Codecov Report

Merging #9958 (d2b15c2) into master (173916e) will decrease coverage by 6.27%.
The diff coverage is 85.71%.

@@             Coverage Diff              @@
##             master    #9958      +/-   ##
============================================
- Coverage     70.46%   64.19%   -6.28%     
+ Complexity     5535     5047     -488     
============================================
  Files          1982     1932      -50     
  Lines        106449   104352    -2097     
  Branches      16131    15908     -223     
============================================
- Hits          75006    66984    -8022     
- Misses        26213    32518    +6305     
+ Partials       5230     4850     -380     

Flag	Coverage Δ
integration1	?
integration2	?
unittests1	67.84% <85.71%> (-0.11%)	⬇️
unittests2	15.82% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
.../transform/function/CoalesceTransformFunction.java	84.23% <85.71%> (-0.30%)	⬇️
...va/org/apache/pinot/common/config/NettyConfig.java	0.00% <0.00%> (-100.00%)	⬇️
...a/org/apache/pinot/common/metrics/MinionMeter.java	0.00% <0.00%> (-100.00%)	⬇️
...g/apache/pinot/common/metrics/ControllerMeter.java	0.00% <0.00%> (-100.00%)	⬇️
.../apache/pinot/common/metrics/BrokerQueryPhase.java	0.00% <0.00%> (-100.00%)	⬇️
.../apache/pinot/common/metrics/MinionQueryPhase.java	0.00% <0.00%> (-100.00%)	⬇️
...ache/pinot/server/access/AccessControlFactory.java	0.00% <0.00%> (-100.00%)	⬇️
...he/pinot/common/messages/SegmentReloadMessage.java	0.00% <0.00%> (-100.00%)	⬇️
...he/pinot/common/messages/TableDeletionMessage.java	0.00% <0.00%> (-100.00%)	⬇️
...pinot/core/data/manager/realtime/TimerService.java	0.00% <0.00%> (-100.00%)	⬇️
... and 484 more

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