Resolve "Follow-up from "Match version in .ruby-version to that in .tool-versions""

What does this merge request do and why?

⚠ This MR needs !2896 (merged) merged first.

This MR adds a new support/ruby-check-versions script and ruby-version CI job that aims to catch when the Ruby version in .ruby-version and .tool-versions differs, e.g.

$ support/ruby-check-versions ; echo $?
ERROR: Ruby version in .ruby-version is '2.7.7' but default Ruby version in .tool-versions is '3.0.5'
1

vs.

$ support/ruby-check-versions ; echo $?
0

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.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Closes #1647 (closed)