Improving iteration time on C# script changes

[stonstad]

From Unity Future .NET Development Status page-48#post-9603908

The biggest active area of development at the moment is our code reloading work - a replacement for domain reloads, with a bit different behavior. We don’t have that entirely finalized yet from the user side, so I don’t want to share too many details that will change. I do expect us to be able to share details about how that will work once things are finalized.