Add unit tests for VexLens normalizer, CPE parser, product mapper, and PURL parser

- Implemented comprehensive tests for VexLensNormalizer including format detection and normalization scenarios.
- Added tests for CpeParser covering CPE 2.3 and 2.2 formats, invalid inputs, and canonical key generation.
- Created tests for ProductMapper to validate parsing and matching logic across different strictness levels.
- Developed tests for PurlParser to ensure correct parsing of various PURL formats and validation of identifiers.
- Introduced stubs for Monaco editor and worker to facilitate testing in the web application.
- Updated project file for the test project to include necessary dependencies.

src/VexLens/StellaOps.VexLens/StellaOps.VexLens.csproj

@@ -16,4 +16,10 @@
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="10.0.0" />
   </ItemGroup>
 
+  <!-- Exclude legacy folders with external dependencies -->
+  <ItemGroup>
+    <Compile Remove="StellaOps.VexLens.Core\**" />
+    <Compile Remove="__Tests\**" />
+  </ItemGroup>
+
 </Project>