Move xterm to a node dependency and remove it from vendor's folder

What does this MR do?

• Moves xterm to a node dependency
• Adds focus on load

Screenshots (if relevant)

How to test locally

1. Set up Gitlab Runner with GDK
2. Download the runner:

cd ~/Downloads
curl -L https://gitlab-runner-downloads.s3.amazonaws.com/25990-ci-web-terminal-2/binaries/gitlab-runner-darwin-amd64 --output runner 
chmod +x  runner

3. Register the runner Set it up to http://localhost:300 and use shell as the executer
4. start the runner ./runner -l debug run --config <path-to-gdk>/gitlab-runner-config.toml

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Conform by the code review guidelines
  • Has been reviewed by a Frontend maintainer
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them

What are the relevant issue numbers?

#25990 (closed) Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/49741