Reveal more generation errors (Test only)

[Tyler-IN]

This PR adds OpenApiGenerator_GenerateMethods and OpenApiGenerator_GenerateConstructors properties to OpenApiGenerator.IntegrationTests.Twitch.Data.csproj to reveal other generation errors.

[Tyler-IN]

Looks like setting <OpenApiGenerator_JsonSerializerContext> to non-empty can cause issues, but that might be intended behavior for that project style.

e.g. rename SourceGenerationContext to TwitchSourceGenerationContext

Might be misinterpretation of how to do it correctly. Looks good otherwise! 👍

[HavenDV]

In order for Trimming to work correctly, you need to use two projects
Here are the instructions
https://github.com/HavenDV/OpenApiGenerator?tab=readme-ov-file#trimming-support
And here is an example of an sdk with trimming support - https://github.com/tryAGI/Ollama

[HavenDV]

When you set OpenApiGenerator_JsonSerializerContext, it will try to pass the internal properties of this one, but this must be generated by another generator (which is part of System.Text.Json). Due to the fact that generators in dotnet cannot see each other's output, you need to use a workaround with the second project