Migrate projects datasource

This change improves the documentation for a GitLab projects data source by adding detailed descriptions to all the available fields. Previously, the documentation only listed field names and types without explaining what each field does. Now each field includes a clear description of its purpose, valid values where applicable, and additional context like which GitLab tiers support certain features. The update also fixes some formatting inconsistencies and corrects a few field type classifications. This makes the documentation much more helpful for developers who need to understand what data they can retrieve about GitLab projects and how to use each field effectively.

Closes #6628 (closed)