Harden Phase 7 teardown sequencing for APIM delete/purge races

[Copilot]

Teardown could advance before Azure finished deleting APIM-backed resource groups, causing purge to run before the APIM soft-delete record existed. This change tightens teardown ordering so purge is gated on actual deletion state, not timing assumptions.

• Deletion completion gate

  • Introduces Wait-ForResourceGroupsDeletion and requires both source/target RGs to be fully deleted before proceeding.
  • Replaces the prior short fixed wait behavior with explicit timeout failure instead of continuing on partial state.

• Soft-delete readiness gate

  • Introduces Wait-ForDeletedApimService to poll deletedservice availability per APIM name + location.
  • Purge now executes only after the soft-deleted service is observable.

• Operational diagnostics

  • Timeout errors now include actionable context (masked RG/APIM identifiers and location) for faster triage.

Wait-ForResourceGroupsDeletion -ResourceGroups @($SourceResourceGroup, $TargetResourceGroup)

Wait-ForDeletedApimService -ServiceName $sourceApimName -ServiceLocation $Location
az apim deletedservice purge --service-name $sourceApimName --location $Location