Measure startup time of GDK in Remote Development workspace

What does this merge request do and why?

This MR measures startup time of GDK in Remote Development workspace.

Related to #1986 (closed)

How to set up and validate locally

1. Open new workspace.
2. Run git checkout 1986-measure-startup-time.
3. Run support/gitlab-remote-development/remote-development-gdk-bootstrap.sh.

Screenshots

Impacted categories

The following categories relate to this merge request:

• 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.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.