Fix table name parsing for window queries

[wolfkill]

Fixes #15204

Summary

• Handle Calcite SqlWindow operands while compiling PinotQuery expressions, so table-name resolution does not crash on OVER window definitions.
• Add regression coverage for extracting table names from a multi-stage LAG(...) OVER (...) query.

Testing

• JAVA_HOME=/opt/homebrew/opt/openjdk@21/libexec/openjdk.jdk/Contents/Home ./mvnw -pl pinot-common -am -Dtest=RequestUtilsTest,TableNameExtractorTest -Dsurefire.failIfNoSpecifiedTests=false test
• git diff --check

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.37%. Comparing base (6bff229) to head (1bfd64f).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
...org/apache/pinot/sql/parsers/CalciteSqlParser.java	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18616      +/-   ##
============================================
- Coverage     64.39%   64.37%   -0.02%     
  Complexity     1137     1137              
============================================
  Files          3336     3336              
  Lines        206096   206100       +4     
  Branches      32145    32147       +2     
============================================
- Hits         132721   132687      -34     
- Misses        62714    62760      +46     
+ Partials      10661    10653       -8     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-21	64.37% <50.00%> (-0.02%)	⬇️
temurin	64.37% <50.00%> (-0.02%)	⬇️
unittests	64.37% <50.00%> (-0.02%)	⬇️
unittests1	56.77% <50.00%> (-0.02%)	⬇️
unittests2	36.94% <0.00%> (-0.02%)	⬇️

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[yashmayya]

LGTM