feat: add multi-threaded evaluation benchmark suite with comprehensive C# implementation (#457)

This commit introduces a complete multi-threaded evaluation benchmark suite for both Rust and C# implementations of Regorus.

- Implemented engine evaluation benchmark with input and engine cloning strategies
- Implemented compiled policy evaluation benchmark with input cloning and shared compiled policy strategies.

- Created EngineEvaluationBenchmark.cs and CompiledPolicyEvaluationBenchmark.cs with time-based execution (3s warmup + 3s evaluation)
- Implemented configuration options matching Rust implementation (useClonedEngines, useSharedPolicies parameters)

- Created markdown analysis documentation with cross-platform performance analysis
- C# seems to achieve 58-89% of Rust performance on test machine.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

benches/evaluation/test_data/inputs/data_sensitivity_input.json

@@ -0,0 +1,13 @@
+{
+  "data": {
+    "type": "user_profile",
+    "classification": "personal",
+    "contains_pii": true,
+    "region": "EU"
+  },
+  "user": {
+    "clearance": "confidential",
+    "location": "EU"
+  },
+  "operation": "read"
+}