chore: repo cleanup and code quality improvements

- Remove global.json (SDK pinning unnecessary)

- Remove nuget.config, move MyGet source to .csproj RestoreAdditionalProjectSources

- Gitignore ndepend/ entirely, move badges to docs/img/

- Update README.md and docs/ndepend.md badge paths

- Add NDepend project property to QuanTAlib.slnx

- Expand .editorconfig ReSharper/diagnostic suppressions

- Use ArgumentOutOfRangeException instead of ArgumentException

- Use discard _ for unused event sender parameters

- Remove quantalib.code-workspace and sonar-suppressions.json

- Add filter signature SVGs

QuanTAlib.slnx

@@ -10,4 +10,7 @@
   <Folder Name="/python/">
     <Project Path="python/python.csproj" />
   </Folder>
+  <Properties Name="NDepend">
+    <Property Name="Project" Value="&quot;.\ndepend\quantalib.ndproj&quot;" />
+  </Properties>
 </Solution>