Add a project and branch/tag picker to the GitLab: Open Repository command

Provides a convenient way to open gitlab-remote URIs without entering them directly. Replaces !328 (closed).

1. Choose how to open the remote

2. Browse projects or enter URL directly

3. Choose a GitLab instance

4. Choose one of your projects

Or enter the name of a public project, e.g. gitlab-org/gitlab

5. Choose a branch or tag

Allow entering a commit sha?

6. Enter a label

The prompt on this one could use some work. The input value defaults to the project's name.

7. Browse the remote