Begin removal of Clusters::Applications::UninstallWorker

What does this MR do and why?

Remove clusters_applications_* code (#366573 - closed) relates to removing clusters_applications_* code, as it is no longer in use and the UI related to it has been removed. We want to break that issue down into several smaller MRs. This MR is the first attempt at removing some of the job code using the approach outlined in this issue.

What this MR does

This MR represents step 1 in the step by step approach outlined above, for 1 Job:

• Noop Clusters::Applications::UninstallWorker#perform.
• Delete Clusters::Applications::DestroyService which is unreachable and enqueues Clusters::Applications::UninstallWorker.
• Delete Clusters::Applications::UninstallService which is only invoked from Clusters::Applications::UninstallWorker.
• Delete unit specs for deleted classes.
• Address any other failing specs impacted.

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.

Related to #366573 (closed)