test(allOf): add comprehensive tests for allOf additionalProperties: false fix
- Add OpenAPI 2.0 test specification with allOf + additionalProperties: false schema
- Add 2.0.x test case to validate fix behavior across all parser versions
- Update snapshots for all parsers showing clean intersection types (Foo & {})
- Validates that empty objects with additionalProperties: false in allOf no longer generate [key: string]: never signatures