.NET Core fsi VS integration : interrupt server

[dsyme]

Related to #2407

Just to mention that the F# Interactive supported by .NET Core is missing some functionality which is currently relevant to hosting F# Interactive inside Visual Studio.

• "Interrupt execution". This is currently implemented by opening a "back door" .NET remoting connection and calling Interrupt.

• There's also dotnet-fsi doesn't allow the use of up-arrow or moving the cursor without --readline #6185 but that's not particularly VS-related

This corresponds to FSI_SERVER.

I don't really care how we implement this functionality - certainly we don't need to use .NET remoting which is not supported in .NET Core - but we should make sure we implement the end-user features as part of the VS integration for .NET Core scripting.

[vzarytovskii]

I think this is done by @KevinRansom via the controlled execution.