Enable starting remote development workspace from gitlab-org/gitlab

Overview

Quoting @mvanremmerden's comment from Slack (internal):

Hey team 👋 Right now to use GitLab Workspaces to make changes to gitlab-org/gitlab, our developers need to start their workspace from gitlab-org/gitlab-development-kit, which is not very clear to our own developers, and also different to how we had set up Gitpod, which people used before we had our own solution with GitLab Workspaces. Is there any chance we could change it to the same way as Gitpod works?

We should enable users to start their workpspaces from gitlab-org/gitlab so they don't have to navigate to gitlab-org/gitlab-development-kit.

Impacted categories

The following categories relate to this issue:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Steps to replicate (optional)

Proposal (optional)

Allow users to start a workspace from gitlab-org/gitlab> (instead of gitlab-org/gitlab-development-kit>)

Steps:

• Move Agent configuration from https://gitlab.com/gitlab-org/gitlab-development-kit/-/tree/main/.gitlab/agents/remote-development to the monolith
• Adjust workspace setup script
  • Skip cloning monolith repo (done by Workspace in postStart hook)
  • Account for the new $HOME (/project/gitlab) and the new folder structure (perhaps symlink to ~/workspace/gitlab-development/gitlab)
• Remove https://gitlab.com/gitlab-org/gitlab-development-kit/-/tree/main/.gitlab/agents/remote-development

Environment (optional)

• Operating system name: <!-- output of `uname -a` command -->
• Architecture: <!-- output of `arch` command -->
• The contents of your gdk.yml (if any)
• Ruby version: <!-- output of `ruby --version` command -->
• GDK version: <!-- output of `git rev-parse --short HEAD` command -->