Add SBOM, symbols, traces, and VEX files for CVE-2022-21661 SQLi case

- Created CycloneDX and SPDX SBOM files for both reachable and unreachable images.
- Added symbols.json detailing function entry and sink points in the WordPress code.
- Included runtime traces for function calls in both reachable and unreachable scenarios.
- Developed OpenVEX files indicating vulnerability status and justification for both cases.
- Updated README for evaluator harness to guide integration with scanner output.

src/Policy/StellaOps.Policy.Engine/Services/PolicyEngineDiagnosticCodes.cs

@@ -0,0 +1,6 @@
+namespace StellaOps.Policy.Engine.Services;
+
+internal static class PolicyEngineDiagnosticCodes
+{
+    public const string CompilationComplexityExceeded = "ERR_POL_COMPLEXITY";
+}