Support frameworks that don't select correct roslyn package

SDKs released before .NET 6 don't select the specific version of roslyn from the nuget, and instead run all of them.

This leads to the generator running multiple times, leading to a compile error.

https://andrewlock.net/supporting-multiple-sdk-versions-in-analyzers-and-source-generators/#supporting-multiple-sdk-versions-and-lighting-up-features

To fix - add some build transitive targets