C#: Run source generators tests in CI

Also fixes ScriptPathAttributeGenerator for generic types and its test.

.github/workflows/linux_builds.yml

@@ -169,6 +169,11 @@ jobs:
           ${{ matrix.bin }} --help
           ${{ matrix.bin }} --headless --test --force-colors
 
+      - name: .NET source generators tests
+        if: ${{ matrix.build-mono }}
+        run: |
+          dotnet test modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests
+
       # Check class reference
       - name: Check for class reference updates
         if: ${{ matrix.doc-test }}