Adds OUTER set operators to parser and type domain

[rchowell]

Issue #, if available:

Part 2 of — #184

Description of changes:

These changes add the OUTER set operators defined in RFC-0007 to the type universe, lexer, and parser.

Have you updated the Unreleased section of CHANGELOG.md with your changes? (y/n), If not, please explain why: No, N/A

Does your PR include any backward-incompatible changes? (y/n), if yes, please explain the reason. In addition, please
also mention any other alternatives you've considered and the reason they've been discarded?: N

For this purpose, we define backward-incompatible changes as changes that—when consumed—can potentially result in 
errors for users that are using our public APIs or the entities that have `public` visibility in our code-base.

Does your PR introduce a new external dependency? (y/n), if yes, please explain the reason. In addition, please
also mention any other alternatives you've considered and the reason they've been discarded?: N

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Merging #678 (7a302e5) into main (9d20e4a) will increase coverage by 0.79%.
The diff coverage is 71.27%.

@@             Coverage Diff              @@
##               main     #678      +/-   ##
============================================
+ Coverage     79.61%   80.40%   +0.79%     
- Complexity     2350     2558     +208     
============================================
  Files           236      240       +4     
  Lines         19358    21003    +1645     
  Branches       3768     4248     +480     
============================================
+ Hits          15411    16888    +1477     
- Misses         2660     2793     +133     
- Partials       1287     1322      +35     

Flag	Coverage Δ
CLI	22.68% <ø> (ø)
EXAMPLES	76.24% <ø> (ø)
EXTENSIONS	69.23% <ø> (ø)
LANG	82.36% <71.27%> (+0.69%)	⬆️
PTS	∅ <ø> (∅)
TEST_SCRIPT	77.98% <ø> (ø)

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

Impacted Files	Coverage Δ
...ng/src/org/partiql/lang/ast/StatementToExprNode.kt	90.38% <0.00%> (-0.76%)	⬇️
.../eval/physical/PhysicalExprToThunkConverterImpl.kt	85.17% <0.00%> (+3.98%)	⬆️
...planner/transforms/AstToLogicalVisitorTransform.kt	90.29% <ø> (+1.65%)	⬆️
lang/src/org/partiql/lang/syntax/SqlLexer.kt	93.54% <ø> (ø)
...ng/src/org/partiql/lang/eval/EvaluatingCompiler.kt	77.60% <14.28%> (-0.10%)	⬇️
...c/org/partiql/lang/prettyprint/ASTPrettyPrinter.kt	79.78% <28.57%> (-1.76%)	⬇️
...ng/src/org/partiql/lang/ast/ExprNodeToStatement.kt	92.95% <86.95%> (+0.03%)	⬆️
lang/src/org/partiql/lang/syntax/LexerConstants.kt	99.14% <100.00%> (+0.04%)	⬆️
lang/src/org/partiql/lang/syntax/SqlParser.kt	82.63% <100.00%> (+4.87%)	⬆️
...ang/src/org/partiql/lang/ast/AstDeserialization.kt	82.03% <0.00%> (-2.23%)	⬇️
... and 16 more

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[alancai98]

Left some comments about the modeling of OUTER in set operators and not needing to support OUTER in the older AST versions. Also noticed that specifying DISTINCT following the set operator results in a parser error.

[alancai98]

Thanks for adding more tests and addressing the feedback. Left a comment about some operators missing from the precedence map and some rewritten SqlParserTest test cases.

[alancai98]