Virtual Registry: Refactor cache purging logic to use a common worker

What does this MR do and why?

This MR consolidates duplicate cache purging logic across Virtual Registries by introducing a common worker class. Previously, both Container and Maven virtual registries had separate but nearly identical MarkEntriesForDestructionWorker classes that performed the same cache entry destruction operations.

What it does:

• Creates a new shared VirtualRegistries::Cache::MarkEntriesForDestructionWorker that handles cache purging for both Container and Maven virtual registries
• Updates all upstream models (VirtualRegistries::Container::Upstream and VirtualRegistries::Packages::Maven::Upstream) to use the common worker
• Changes the worker parameter from upstream ID to Global ID string for polymorphic support
• The 1st step from the docs guide towards removing the existing package-specific workers.

References

• Extract common code for cache purging (#582162 - closed) • Moaz Khalifa • 18.7
• Add delete cache API for container virtual regi... (!213785 - merged) • Adie (she/her) • 18.7
• Add purge cache functionality for Maven virtual... (!195815 - merged) • Moaz Khalifa • 18.2

Screenshots or screen recordings

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How to set up and validate locally

Follow these steps: !213785 (merged)

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Related to #582162 (closed)