feat(cosmosdb): improve SQL parser compatibility for all 13 query feature areas

[h3n4l]

Summary

• Rewrite CosmosDB ANTLR4 grammar to support all 13 query feature areas that were failing with syntax errors (BYT-9043)
• Merge split scalar_expression / scalar_expression_in_where into a single unified scalar_expression rule
• Add 18 new test SQL examples covering all feature areas

Grammar Changes

Lexer (CosmosDBLexer.g4):

• Add missing keyword tokens: IN, BETWEEN, TOP, VALUE, ORDER, BY, GROUP, OFFSET, LIMIT, ASC, DESC, EXISTS, LIKE, HAVING, JOIN
• Add != operator (NOT_EQUAL_OPERATOR)
• Fix IDENTIFIER rule to allow leading underscore (for system properties like _ts, _etag, _rid)

Parser (CosmosDBParser.g4):

• Unify scalar_expression and scalar_expression_in_where into single scalar_expression (resolves the TODO in the grammar)
• Add SELECT TOP N, SELECT VALUE, SELECT DISTINCT VALUE support
• Add ORDER BY clause with ASC/DESC
• Add GROUP BY and HAVING clauses
• Add OFFSET ... LIMIT ... pagination
• Add IN, BETWEEN, LIKE, NOT expression support
• Add EXISTS subquery and scalar subquery support
• Add JOIN clause for intra-document joins
• Fix object_constant_field_pair to use COLON_SYMBOL instead of COMMA_SYMBOL
• Add identifier rule allowing keywords as property names/aliases
• Support empty function argument lists and COUNT(*)

13 Feature Areas Now Supported

1. SELECT TOP N
2. WHERE with !=, IN, BETWEEN, underscore fields
3. Functions and arithmetic in SELECT projections
4. ORDER BY
5. Aggregation functions (COUNT, SUM, AVG, MIN, MAX)
6. GROUP BY
7. String functions (UPPER, LOWER, LENGTH)
8. Math functions (ROUND)
9. Type checking functions (IS_STRING, IS_NUMBER, IS_DEFINED)
10. SELECT DISTINCT VALUE
11. SELECT VALUE
12. OFFSET ... LIMIT ... pagination
13. Geo-spatial functions with JSON object literals

Test plan

• All 5 existing parser tests pass
• All 18 new test SQL examples parse without errors (23 total)
• make build generates parser successfully
• make test passes

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR expands the Cosmos DB SQL ANTLR grammar and adds example queries to validate parsing of additional query constructs.

Changes:

• Extended SELECT grammar to support TOP, VALUE, GROUP BY/HAVING, ORDER BY, OFFSET ... LIMIT ..., and JOIN.
• Unified/expanded scalar_expression to cover more operators and expression forms (e.g., IN, BETWEEN, LIKE, EXISTS, object/array creation).
• Added a suite of example .sql files that are exercised by parser_test.go.

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
cosmosdb/CosmosDBParser.g4	Adds/updates core parser rules for new clauses and expressions.
cosmosdb/CosmosDBLexer.g4	Adds new keyword/operator tokens and broadens identifier start chars (e.g., _).
cosmosdb/cosmosdb_lexer.go	Regenerated lexer output reflecting lexer grammar changes.
cosmosdb/cosmosdbparser_visitor.go	Regenerated visitor interface for new/removed parser rules.
cosmosdb/cosmosdbparser_listener.go	Regenerated listener interface for new/removed parser rules.
cosmosdb/cosmosdbparser_base_visitor.go	Regenerated base visitor implementations.
cosmosdb/cosmosdbparser_base_listener.go	Regenerated base listener implementations.
cosmosdb/examples/aggregation.sql	Example for aggregation COUNT.
cosmosdb/examples/between_expression.sql	Example for BETWEEN.
cosmosdb/examples/distinct_value.sql	Example for DISTINCT VALUE.
cosmosdb/examples/geospatial.sql	Example for geospatial function + object/array literals.
cosmosdb/examples/group_by.sql	Example for GROUP BY with aggregation.
cosmosdb/examples/in_expression.sql	Example for IN (...).
cosmosdb/examples/math_functions.sql	Example for numeric + conversion functions.
cosmosdb/examples/not_equal.sql	Example for !=.
cosmosdb/examples/offset_limit.sql	Example for ORDER BY ... OFFSET ... LIMIT ....
cosmosdb/examples/order_by.sql	Example for ORDER BY.
cosmosdb/examples/select_functions.sql	Example for scalar functions and arithmetic in projection.
cosmosdb/examples/select_top.sql	Example for TOP.
cosmosdb/examples/string_functions.sql	Example for string functions.
cosmosdb/examples/type_check_functions.sql	Example for type-check functions.
cosmosdb/examples/underscore_fields.sql	Example for system properties like _ts, _etag, _rid.
cosmosdb/examples/value_count.sql	Example for SELECT VALUE COUNT(1).
cosmosdb/examples/value_keyword.sql	Example for SELECT VALUE projection.
cosmosdb/examples/where_operators.sql	Example for WHERE with != and _ts filtering.

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