Add unit tests for RancherHubConnector and various exporters

- Implemented tests for RancherHubConnector to validate fetching documents, handling errors, and managing state.
- Added tests for CsafExporter to ensure deterministic serialization of CSAF documents.
- Created tests for CycloneDX exporters and reconciler to verify correct handling of VEX claims and output structure.
- Developed OpenVEX exporter tests to confirm the generation of canonical OpenVEX documents and statement merging logic.
- Introduced Rust file caching and license scanning functionality, including a cache key structure and hash computation.
- Added sample Cargo.toml and LICENSE files for testing Rust license scanning functionality.

src/Scanner/__Libraries/StellaOps.Scanner.Analyzers.Lang.Rust/Internal/RustFileCacheKey.cs

@@ -0,0 +1,74 @@
+using System.Security;
+
+namespace StellaOps.Scanner.Analyzers.Lang.Rust.Internal;
+
+internal readonly struct RustFileCacheKey : IEquatable<RustFileCacheKey>
+{
+    private readonly string _normalizedPath;
+    private readonly long _length;
+    private readonly long _lastWriteTicks;
+
+    private RustFileCacheKey(string normalizedPath, long length, long lastWriteTicks)
+    {
+        _normalizedPath = normalizedPath;
+        _length = length;
+        _lastWriteTicks = lastWriteTicks;
+    }
+
+    public static bool TryCreate(string path, out RustFileCacheKey key)
+    {
+        key = default;
+
+        if (string.IsNullOrWhiteSpace(path))
+        {
+            return false;
+        }
+
+        try
+        {
+            var info = new FileInfo(path);
+            if (!info.Exists)
+            {
+                return false;
+            }
+
+            var normalizedPath = OperatingSystem.IsWindows()
+                ? info.FullName.ToLowerInvariant()
+                : info.FullName;
+
+            key = new RustFileCacheKey(normalizedPath, info.Length, info.LastWriteTimeUtc.Ticks);
+            return true;
+        }
+        catch (IOException)
+        {
+            return false;
+        }
+        catch (UnauthorizedAccessException)
+        {
+            return false;
+        }
+        catch (SecurityException)
+        {
+            return false;
+        }
+        catch (ArgumentException)
+        {
+            return false;
+        }
+        catch (NotSupportedException)
+        {
+            return false;
+        }
+    }
+
+    public bool Equals(RustFileCacheKey other)
+        => _length == other._length
+           && _lastWriteTicks == other._lastWriteTicks
+           && string.Equals(_normalizedPath, other._normalizedPath, StringComparison.Ordinal);
+
+    public override bool Equals(object? obj)
+        => obj is RustFileCacheKey other && Equals(other);
+
+    public override int GetHashCode()
+        => HashCode.Combine(_normalizedPath, _length, _lastWriteTicks);
+}