Launch Gitpod from the MR page

Problem to solve

When reviewing a merge request, it is often necessary to review the changes in a local development environment. The Gitpod integration makes it easier to manage your development environments by creating a cloud-based IDE available wherever you need it. It can, however, be cumbersome to launch Gitpod targeting a specific branch and merge request.

Proposal

Add a button to Open Gitpod in the merge request view, alongside the Open in Web IDE button. Using the same split button drop-down pattern we've introduced in the repository view, we can let users select the environment in which they want to edit. For smaller, simpler edits, the Web IDE may be preferable. For more elaborate edits or those that require code compilation, launching Gitpod is just as easy.