Update Pigeon to v18

[evil159]

What does this pull request do?

Updates Pigeon-generated code with v18.0.0 changes.

What is the motivation and context behind this change?

Keeping dependencies up to date.

Pull request checklist:

• [ ] Add a changelog entry.
• [ ] Write tests for all new functionality. If tests were not written, please explain why.
• [ ] Add documentation comments for any added or updated public APIs.