[Multi-stage] Fix literal handling

[Jackie-Jiang]

• Ensure literal is properly handled for all types
• Explicitly handle SYMBOL and NULL
• Also fixes a minor bug in stats collection which can cause NPE after query fails

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 62.81407% with 74 lines in your changes missing coverage. Please review.

Project coverage is 62.05%. Comparing base (59551e4) to head (908f611).
Report is 582 commits behind head on master.

Files	Patch %	Lines
...pache/pinot/common/utils/request/RequestUtils.java	52.30%	25 Missing and 6 partials ⚠️
.../planner/serde/ProtoExpressionToRexExpression.java	43.33%	16 Missing and 1 partial ⚠️
...inot/query/planner/logical/RexExpressionUtils.java	77.77%	5 Missing and 9 partials ⚠️
.../planner/serde/RexExpressionToProtoExpression.java	61.90%	7 Missing and 1 partial ⚠️
.../query/planner/logical/RelToPlanNodeConverter.java	0.00%	1 Missing and 2 partials ⚠️
...core/query/executor/ServerQueryExecutorV1Impl.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13344      +/-   ##
============================================
+ Coverage     61.75%   62.05%   +0.30%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2545     +109     
  Lines        133233   139720    +6487     
  Branches      20636    21675    +1039     
============================================
+ Hits          82274    86702    +4428     
- Misses        44911    46456    +1545     
- Partials       6048     6562     +514     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	62.02% <62.81%> (+0.31%)	⬆️
java-21	61.93% <62.81%> (+0.31%)	⬆️
skip-bytebuffers-false	62.04% <62.81%> (+0.29%)	⬆️
skip-bytebuffers-true	35.09% <62.81%> (+7.37%)	⬆️
temurin	62.05% <62.81%> (+0.30%)	⬆️
unittests	62.04% <62.81%> (+0.30%)	⬆️
unittests1	46.59% <62.81%> (-0.30%)	⬇️
unittests2	27.74% <0.00%> (+0.01%)	⬆️

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