Modify `update_project_templates` rake task to include data other than just commits

Based on https://gitlab.com/gitlab-org/project-templates/contributing, we use the rake task bin/rake gitlab:update_project_templates, to create a new project template.

But this rake task currently only supports creating a template with commit data in them.

We are currently seeing the need to create new project templates with more data in them, like issues and labels as described in #13756 (closed).

Hence, we should modify this rake task to support such use-cases.