feat: Add search_type as attribute to search endpoints

This change adds support for specifying different search types when using GitLab's search functionality. The code introduces three search options - basic, advanced, and Zoekt - that users can choose from to control how their searches are performed. The update includes the necessary data structures to handle these search types and updates the test code to demonstrate using the basic search option. This gives developers more control over search behavior when building applications that integrate with GitLab's search features.