[Multi-stage] Clean up RelNode to Operator handling

[Jackie-Jiang]

Clean up the flow from RelNode from planner side to MultiStageOperator on the executor side:

• Cleanup unnecessary fields and conversions in PlanNode, and keep it close to information from Calcite RelNode
• Unify the constructor for PlanNode
• Cleanup plan.proto to reflect the changes in PlanNode
• Cleanup MultiStageOperator fields and unnecessary conversions
• Reduce the memory allocation
• Cleanup all the MultiStageOperator tests

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 71.44120% with 323 lines in your changes missing coverage. Please review.

Project coverage is 62.00%. Comparing base (59551e4) to head (eaec88c).
Report is 565 commits behind head on master.

Files	Patch %	Lines
...inot/query/planner/serde/PlanNodeDeserializer.java	69.14%	41 Missing and 13 partials ⚠️
...hysical/colocated/GreedyShuffleRewriteVisitor.java	0.00%	35 Missing ⚠️
.../pinot/query/planner/serde/PlanNodeSerializer.java	72.95%	26 Missing and 7 partials ⚠️
...che/pinot/query/planner/logical/RexExpression.java	27.27%	6 Missing and 10 partials ⚠️
...che/pinot/query/planner/plannode/ExchangeNode.java	43.47%	13 Missing ⚠️
...not/query/planner/plannode/MailboxReceiveNode.java	57.69%	4 Missing and 7 partials ⚠️
.../pinot/query/planner/plannode/MailboxSendNode.java	54.16%	4 Missing and 7 partials ⚠️
...pache/pinot/query/planner/plannode/WindowNode.java	61.53%	4 Missing and 6 partials ⚠️
...operator/window/value/LeadValueWindowFunction.java	0.00%	10 Missing ⚠️
.../query/planner/logical/RelToPlanNodeConverter.java	91.74%	4 Missing and 5 partials ⚠️
... and 29 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13325      +/-   ##
============================================
+ Coverage     61.75%   62.00%   +0.25%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2545     +109     
  Lines        133233   139570    +6337     
  Branches      20636    21648    +1012     
============================================
+ Hits          82274    86545    +4271     
- Misses        44911    46480    +1569     
- Partials       6048     6545     +497     

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	61.98% <71.44%> (+0.27%)	⬆️
java-21	61.89% <71.44%> (+0.27%)	⬆️
skip-bytebuffers-false	61.99% <71.44%> (+0.25%)	⬆️
skip-bytebuffers-true	61.88% <71.44%> (+34.15%)	⬆️
temurin	62.00% <71.44%> (+0.25%)	⬆️
unittests	62.00% <71.44%> (+0.25%)	⬆️
unittests1	46.52% <71.44%> (-0.37%)	⬇️
unittests2	27.76% <0.00%> (+0.03%)	⬆️

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