fix: sync KRM function resource deletions in specializers

[pulkitvats2007-crypto]

Summary

Fixes a critical issue where KRM function pipelines were unable to delete resources due to append-only reconciliation logic in the Specializer controllers.

Previously, controllers (generic-specializer, ipam-specializer, vlan-specializer) rebuilt prr.Spec.Resources by iterating only over rl.Items. Since deleted resources are absent from rl.Items, they were never removed from the map, resulting in stale ("ghost") resources persisting in the package.

This PR introduces explicit deletion synchronization:

• Capture original resource paths before running the KRM pipeline.
• Capture surviving paths after pipeline execution.
• Diff both sets and explicitly remove missing entries using delete().

This ensures full state reconciliation (create/update/delete) instead of append-only behavior.

---

Bug

Root Cause:
The controller assumed that iterating over the mutated rl.Items was sufficient to sync state back to prr.Spec.Resources. This ignored deletion semantics entirely.

Resulting Issue:

• Resources deleted by KRM functions (e.g., via condkptsdk GC) were silently retained.
• No errors or signals were emitted, leading to misleading "successful" reconciliations.

---

Fix

• Added path tracking (originalPaths, survivingPaths)
• Implemented syncDeletedResources helper to reconcile deletions
• Applied fix consistently across:
  • generic-specializer
  • ipam-specializer
  • vlan-specializer
• Added unit tests to prevent regression

---

Impact

• Eliminates ghost resources from PackageRevisions
• Restores correct KRM deletion semantics
• Prevents downstream GitOps drift and infra conflicts (e.g., duplicate IPs)
• Improves reliability of Nephio automation in dynamic/topology-changing environments

[nephio-prow]

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[nephio-prow]

Hi @pulkitvats2007-crypto. Thanks for your PR.

I'm waiting for a nephio-project member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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