Log QA resource reuse

What does this MR do and why?

Changes the debug log message shown when a resource is fabricated.

• "Built" as previously, when a resource is created.
• "Retrieved" when an existing resource is fetched.
• "Retrieved for reuse" when an existing resource is fetched as a reusable resource.

Adds a ReusableGroup class so that ResuableProject is truly reusable (otherwise ResuableProject would create a new group in a different project each time).

Part of https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1032

Examples

Previously, the debug log for fabricating a resource always said Built, like this:

==> Built a QA::Resource::Project with full_path 'gitlab-qa-sandbox-group/contribution_analytics-a630bee295505362/contribution_analytics-d94f429a07bfa22a' via api in 0.607407829 seconds

Now it still says Built when a new resource is created, but if an existing resource is fetched (instead of creating a new one), it says something like:

==> Retrieved a QA::Resource::Group with full_path 'gitlab-qa-sandbox-group/qa-test-2022-01-10-23-52-28-6e54ea33b183dbe5' via api in 1.244220592 seconds

And if it's a reusable resource:

==> Retrieved for reuse a QA::Resource::ReusableGroup with full_path 'gitlab-qa-sandbox-group/reusable_group' via api in 0.804077896 seconds

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.