Add test coverage for postgres upgrade on macOS

What does this merge request do and why?

Add a new test that installs the GDK and attemps to upgrade the postgres version every time there is a change in the .tool-versions file.
This will validate that a postgres upgrade won't break local development setups.
See Add a test case to cover an update or upgrade o... (#2962 - closed).

How to validate

Please inspect the postgres-upgrade:macos job in the novel stage in this pipeline: https://gitlab.com/gitlab-org/gitlab-development-kit/-/pipelines/2017303925.

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 MR references an issue describing the change.
• 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.

Closes #2962 (closed).