feat(snowflake): sync upstream grammar and fix task scripting parse

[h3n4l]

Summary

• sync snowflake grammar sources to latest upstream antlr/grammars-v4
• keep Bytebase-specific compatibility behavior while syncing:
  • allow bare file:// in FILE_PATH
  • keep UNDROP DYNAMIC TABLE
  • keep non-reserved keyword supplementation via build_id_contains_non_reserved_keywords.py
• fix BYT-3534 parsing gap for Snowflake task scripting bodies in CREATE/ALTER TASK ... AS ...:
  • AS BEGIN ... END
  • AS DECLARE ... BEGIN ... END
• add regression examples:
  • snowflake/examples/create_pipe.sql
  • snowflake/examples/task_scripting.sql

Test Plan

• go test ./snowflake -run 'TestSnowflakeSQLParser/examples/create_pipe.sql$' -count=1
• go test ./snowflake -run 'TestSnowflakeSQLParser/examples/task_scripting.sql$' -count=1
• go run /tmp/check_byt3534_bytebase.go
• go test ./snowflake -count=1
• go test ./...

[Copilot]

Pull request overview

This PR syncs the Snowflake grammar to the latest upstream antlr/grammars-v4 repository while maintaining Bytebase-specific compatibility behaviors. The main enhancement is fixing BYT-3534 by adding support for Snowflake task scripting bodies in CREATE/ALTER TASK statements.

Changes:

• Syncs Snowflake grammar sources to latest upstream while preserving Bytebase customizations (bare file:// support, UNDROP DYNAMIC TABLE, non-reserved keyword supplementation)
• Adds parsing support for task scripting blocks: AS BEGIN ... END and AS DECLARE ... BEGIN ... END
• Improves Python build script to handle upstream grammar formatting changes
• Regenerates all Go parser artifacts (visitor, listener, base implementations) with hundreds of new grammar rule methods

Reviewed changes

Copilot reviewed 8 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
snowflake/examples/task_scripting.sql	New regression test demonstrating task scripting with BEGIN/END and DECLARE blocks
snowflake/examples/create_pipe.sql	New regression test for CREATE PIPE with various stage configurations
snowflake/build_id_contains_non_reserved_keywords.py	Enhanced to handle upstream grammar formatting (indentation, comments between rule name and colon)
snowflake/snowflakeparser_visitor.go	Auto-generated: adds ~200 new Visit methods for new grammar rules
snowflake/snowflakeparser_listener.go	Auto-generated: adds ~200 new Enter/Exit methods for new grammar rules
snowflake/snowflakeparser_base_visitor.go	Auto-generated: adds ~200 new Visit method implementations
snowflake/snowflakeparser_base_listener.go	Auto-generated: adds ~200 new Enter/Exit method stubs

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