feat: add support for GitHub and gitlab in helper

[daniel-cit]

This PR adds support for GitHub Action and GitLab workflows deploy in deploy helper

[daniel-cit]

@apeabody Could you PTAL?

[apeabody]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for GitHub Actions and GitLab CI/CD as alternatives to Google Cloud Build for the deployment helper. The changes are extensive, involving significant refactoring to modularize CI/CD-specific configurations, the introduction of an Executor interface to abstract CI/CD system interactions, and updates to documentation and helper scripts. The overall design is solid. However, I've identified a few critical issues: a potential modification of the source code directory, a security risk of leaking secrets in logs, and a bug in the build-type selection script that could lead to an inconsistent state. Addressing these points will greatly improve the robustness and security of the new functionality.