feat(azure): add AZUREVIRTUALNETWORKS candidate relationship for cross-subscription resolution (NR-582475, NR-584562)

Adds a candidate relationship definition so the Entity Platform can
resolve Azure VNet targets across subscriptions and across NR accounts
natively, using the tag `azure.resourceId` that AZUREVIRTUALNETWORKS
entities already carry.

Files:
- relationships/candidates/AZUREVIRTUALNETWORKS.yml
  Lookup on the `azure.resourceId` tag. `onMiss: CREATE_UNINSTRUMENTED`
  produces an `UNINSTRUMENTED-AZUREVIRTUALNETWORKS` placeholder when the
  target subscription is not yet integrated / scanned; the platform
  auto-swaps to the real `INFRA-AZUREVIRTUALNETWORKS` entity when it
  later appears.
- entity-types/uninstrumented-azurevirtualnetworks/definition.yml
  Required by the CREATE_UNINSTRUMENTED action. Owned by CMP.

Producer: azure-configuration-fetcher will emit CandidateRelationship
messages against this category behind a per-NR-account feature flag
that defaults to off.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: nr-siranjeevi

entity-types/uninstrumented-azurevirtualnetworks/definition.yml

@@ -0,0 +1,14 @@
+domain: UNINSTRUMENTED
+type: AZUREVIRTUALNETWORKS
+
+configuration:
+  entityExpirationTime: DAILY
+  alertable: false
+
+synthesis:
+  # Uninstrumented can't use synthesis
+  disabled: true
+
+ownership:
+  primaryOwner:
+    teamName: "Cloud Monitoring Platform"

relationships/candidates/AZUREVIRTUALNETWORKS.yml

@@ -0,0 +1,16 @@
+category: AZUREVIRTUALNETWORKS
+lookups:
+  - entityTypes:
+      - domain: INFRA
+        type: AZUREVIRTUALNETWORKS
+    tags:
+      matchingMode: ALL
+      predicates:
+        - tagKeys: ["azure.resourceId"]
+          field: azureResourceId
+    onMatch:
+      onMultipleMatches: RELATE_ALL
+    onMiss:
+      action: CREATE_UNINSTRUMENTED
+      uninstrumented:
+        type: AZUREVIRTUALNETWORKS