feat: add GoogleSQL parser to monorepo (#29)

This commit adds the GoogleSQL (BigQuery) parser from the standalone google-sql-parser repository into the unified parser monorepo.

Changes:
- Added GoogleSQL grammar files (GoogleSQLLexer.g4, GoogleSQLParser.g4)
- Added test infrastructure with 72 example SQL files (including TPC-H queries and ZetaSQL test data)
- Created Makefile for building and testing the parser
- Updated package names from 'parser' to 'googlesql'
- Updated import paths to github.com/bytebase/parser/googlesql
- Updated CI workflow to include googlesql in the test matrix
- Generated parser files using ANTLR 4 with Go target
- All 72 tests passing successfully

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: h3n4l

.github/workflows/tests.yml

@@ -34,7 +34,7 @@ jobs:
         id: set-matrix
         run: |
           # List of all available parsers
-          ALL_PARSERS="redshift postgresql cql snowflake tsql doris trino plsql"
+          ALL_PARSERS="redshift postgresql cql snowflake tsql doris trino plsql googlesql"
           # Add more parsers here as they are added to the repository
           # ALL_PARSERS="redshift mysql postgresql"