feat(e2e): add Istio service mesh integration test profile

Implement comprehensive E2E testing profile for Istio service mesh integration with Semantic Router:

- Add Istio profile with 4 Istio-specific tests and 13 common tests (17 total)
- Deploy Semantic Router with Istio sidecar injection and service mesh features
- Integrate Envoy Gateway for ExtProc communication alongside Istio mesh capabilities
- Deploy vLLM backend via Gateway API resources with AIServiceBackend CRDs
- Add keyword routing support (urgent_request and sensitive_data decisions)
- Fix Istio test namespace resolution to use vllm-semantic-router-system
- All 17 tests passing with 100% success rate in local testing

Test coverage includes:
- Istio sidecar injection and health verification
- Traffic routing through Istio ingress gateway
- mTLS verification between services
- Distributed tracing and observability
- Chat completions, stress tests, and domain classification
- Plugin chain execution, PII/jailbreak detection, semantic caching

Signed-off-by: Asaad Balum <asaad.balum@gmail.com>

Author: asaadbalum

e2e/profiles/ai-gateway/values.yaml

@@ -383,6 +383,48 @@ config:
             system_prompt: "You are a thinking expert, should think multiple steps before answering. Please answer the question step by step."
             mode: "replace"
 
+    - name: urgent_request
+      description: "Urgent requests requiring immediate attention"
+      priority: 30
+      rules:
+        operator: "OR"
+        conditions:
+          - type: "keyword"
+            name: "urgent_keywords"
+      modelRefs:
+        - model: base-model
+          lora_name: general-expert
+          use_reasoning: false
+      plugins:
+        - type: "system_prompt"
+          configuration:
+            enabled: true
+            system_prompt: "You are handling an urgent request. Prioritize quick and direct responses."
+            mode: "replace"
+
+    - name: sensitive_data
+      description: "Queries containing sensitive data keywords (SSN and credit card)"
+      priority: 40
+      rules:
+        operator: "AND"
+        conditions:
+          - type: "keyword"
+            name: "sensitive_keywords"
+      modelRefs:
+        - model: base-model
+          lora_name: general-expert
+          use_reasoning: false
+      plugins:
+        - type: "pii"
+          configuration:
+            enabled: true
+            pii_types_allowed: []
+        - type: "system_prompt"
+          configuration:
+            enabled: true
+            system_prompt: "You are handling a query with sensitive data. Be cautious and provide security-focused guidance."
+            mode: "replace"
+
     - name: other_decision
       description: "General knowledge and miscellaneous topics"
       priority: 1
@@ -478,7 +520,17 @@ config:
   keyword_rules:
     - name: "thinking"
       operator: "OR"
-      keywords: ["urgent", "immediate", "asap", "think", "careful"]
+      keywords: ["think", "careful"]
+      case_sensitive: false
+    
+    - name: "urgent_keywords"
+      operator: "OR"
+      keywords: ["urgent", "immediate", "asap", "emergency"]
+      case_sensitive: false
+    
+    - name: "sensitive_keywords"
+      operator: "AND"
+      keywords: ["SSN", "credit card"]
       case_sensitive: false