[tests] Workload tests follow up

[radical]

• Remove unused workload install target
• BuildEnvironment: always clean the local nuget cache on CI
• Move all the RequiresDocker attribute classes to the Common directory
• Improve failure message for workload tests when sdk+workload is not installed
• Handle IOExceptions when deleting testroot to avoid failing the tests if something is in use by a running process
• Install playwright dependencies on windows

Microsoft Reviewers: Open in CodeFlow