Introduce GDK::Execute::Rake adapter

What does this merge request do and why?

This introduces a centralized way to call Rake tasks from inside GDK.

With the new implementation, we are also ensuring both installations with asdf and the ones who opted out have a way to call rake tasks that works and don't conflict with existing Bundler usage.

Existing code has been refactored to use the new implementation.

How to set up and validate locally

Try to execute any code that relies on executing a rails rake task through the GDK codebase, as an example:

make bootstrap-rails

and

rake gitlab-db-migrate

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.