12.0.0-alpha03

We no longer provide many NuGet packages. It's very hard for developer users to choose!

Now, Just package reference dotnetCampus.LatestCSharpFeatures and everything works without any extra dependency.

<!-- Since dotnetCampus.LatestCSharpFeatures only contains source generators, it does not introduce any runtime dependencies.
     We can set it to PrivateAssets="all" to avoid passing it on to other projects. -->
<PackageReference Include="dotnetCampus.LatestCSharpFeatures" Version="12.0.0-alpha03" PrivateAssets="all" />