Similar to https://github.com/dotnet/roslyn-analyzers/blob/main/src/Microsoft.CodeAnalysis.Analyzers/UnitTests/MetaAnalyzers/MissingDiagnosticAnalyzerAttributeRuleTests.cs, but for source generators, which require [GeneratorAttribute](https://github.com/dotnet/roslyn/blob/main/src/Compilers/Core/Portable/SourceGeneration/GeneratorAttribute.cs). Suggested this once I saw https://github.com/YairHalberstadt/SpanLinq/blob/16a309bc7e8a18b3ab8735b8ba57d6f49fcdaf31/SpanLinq/SourceGenerator.cs#L13-L14.
Similar to https://github.com/dotnet/roslyn-analyzers/blob/main/src/Microsoft.CodeAnalysis.Analyzers/UnitTests/MetaAnalyzers/MissingDiagnosticAnalyzerAttributeRuleTests.cs, but for source generators, which require GeneratorAttribute.
Suggested this once I saw https://github.com/YairHalberstadt/SpanLinq/blob/16a309bc7e8a18b3ab8735b8ba57d6f49fcdaf31/SpanLinq/SourceGenerator.cs#L13-L14.