Add duration to debug output in `execute` method

What does this merge request do and why?

This MR logs the duration of commands in the execute method's debug output. This helps identify the most time-consuming commands within targets in Makefiles.

Related to #2057 (closed)

How to set up and validate locally

1. git checkout 2057-add-duration-to-debug-output
2. GDK_DEBUG=true
3. make gitlab-update

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.