Removed NAry operator in SqlParser.kt

[lziq]

Motivation:
Currently, part of parser's code still uses NAry, which are ExprNode operators. We need to remove them as well.

[codecov-commenter]

Codecov Report

Merging #534 (fc51fcc) into deprecate-exprnode (8726cb9) will decrease coverage by 0.01%.
The diff coverage is 85.71%.

@@                   Coverage Diff                    @@
##             deprecate-exprnode     #534      +/-   ##
========================================================
- Coverage                 80.38%   80.36%   -0.02%     
  Complexity                 1680     1680              
========================================================
  Files                       196      196              
  Lines                     14413    14411       -2     
  Branches                   2984     2983       -1     
========================================================
- Hits                      11586    11582       -4     
- Misses                     1855     1858       +3     
+ Partials                    972      971       -1     

Flag	Coverage Δ
CLI	26.53% <ø> (ø)
EXAMPLES	74.71% <ø> (ø)
LANG	82.11% <85.71%> (-0.02%)	⬇️
PTS	∅ <ø> (∅)
TEST_SCRIPT	76.92% <ø> (ø)

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Impacted Files	Coverage Δ
lang/src/org/partiql/lang/syntax/SqlParser.kt	76.74% <85.71%> (-0.10%)	⬇️
lang/src/org/partiql/lang/ast/ast.kt	86.05% <0.00%> (-0.20%)	⬇️

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