Support Spark SQL Hints

[shangyian]

Summary

This change adds support for parsing Spark SQL hints using the ANTLR parser and our custom SQL AST.

The following changes were made:

1. Replaced the Spark ANTLR grammars with the latest versions:
   • SqlBaseLexer
   • SqlBaseParser
2. Regenerated the ANTLR parser based on the modified grammar with antlr4 -Dlanguage=Python3 -visitor SqlBaseLexer.g4 SqlBaseParser.g4 -o generated.

3. Modified the generated grammar to support hints. There were a few issues with hints previously:

   • The isHint() method was entirely in Java, so I converted it manually to Python-compatible code.
   • Java has a char type which can be used to compare ascii values of characters with integers, but this comparison needs to be done explicitly in Python with chr(...)

   • The final isHint() method looks like this:

     """
     This method will be called when we see '/*' and try to match it as a bracketed comment.
     If the next character is '+', it should be parsed as hint later, and we cannot match
     it as a bracketed comment.
     
     Returns true if the next character is '+'.
     """
     def isHint(self) -> bool:
         nextChar = self._input.LA(1)
         if chr(nextChar) == '+':
             return True
         else:
             return False

4. Added a Hint tree node to the AST to store parsed hint statements. Also added a list of hints to SelectExpression.

Test Plan

Added some tests for various Spark hints pulled from https://spark.apache.org/docs/latest/sql-ref-syntax-qry-select-hints.html

• [ ] PR has an associated issue: #1026
• [ ] make check passes
• [ ] make test shows 100% unit test coverage

Deployment Plan

N/A

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