Move Gitpod scripts to gitlab-development-kit repository

What does this MR do?

After the Gitpod specific commands were moved over to separate scripts in gitlab-org/gitlab-development-kit (gitlab-development-kit@3578ba9e), this is the follow-up MR to call these scripts when setting up Gitpod from the gitlab-org/gitlab repository.

The original change was in !45421 (closed), but because I couldn't make changes to the fork and didn't want to disturb him while he is ooo, I opened this new MR that includes both the initial changes as well as the newly generated image.

Fixes #268218 (closed).