Update Roslyn packages to their latest version #814
Description
This is a breaking change because it means that the source generator only runs on newer versions of the .NET SDK and Visual Studio.
There's a handy table that maps Roslyn package version to VS version. Then there's a second table that maps .NET SDK versions to VS versions.
I would like to update to 4.3.1 at minimum because that's the version that introduces context.SyntaxProvider.ForAttributeWithMetadataName.
If we still want to support the .NET 8 SDK, we can update to 4.11.0 at max. We'd support Visual Studio 2022 version 17.11 and upwards.