feat: add GoogleSQL parser to monorepo

[h3n4l]

Summary

• Migrates the GoogleSQL (BigQuery) parser from standalone google-sql-parser repository
• Adds comprehensive test coverage with 72 SQL example files including TPC-H queries
• Updates CI workflow to include googlesql in test matrix
• All tests passing successfully

Changes

• Added GoogleSQL grammar files (GoogleSQLLexer.g4, GoogleSQLParser.g4)
• Added 72 test examples:
  • 1 custom easy.sql example
  • 22 TPC-H benchmark queries from ZetaSQL
  • 49 ZetaSQL parser test data files covering DDL, DML, and other SQL statements
• 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 .github/workflows/tests.yml to include googlesql parser
• Generated parser files using ANTLR 4 with Go target

Test plan

• All 72 GoogleSQL parser tests passing
• Parser generation successful with ANTLR 4
• CI workflow updated to include googlesql parser
• Package names and imports updated correctly

🤖 Generated with Claude Code