[server] Delete prebuild records when purging workspaces

[easyCZ]

Description

When we delete Workspaces, we also need to delete corresponding prebuilds when the Workspace is based on a prebuild.

Related Issue(s)

• Depends on https://github.com/gitpod-io/gitpod/pull/13165

How to test

Release Notes

NONE

Documentation

Werft options:

• [ ] /werft with-preview
• [ ] /werft with-integration-tests=all Valid options are all, workspace, webapp, ide

[easyCZ]

/werft run

:+1: started the job as gitpod-build-mp-gc-delete-prebuilds.5 (with .werft/ from main)