For some reason `func pack` doesn't support C# in-process projects

[ggailey777]

We should expose and document the func pack command (as suggested here by Ahmed), since it's useful for creating deployment packages manually outside of a deployment process. This is beneficial when creating one-off remote deployment package to enable run from package URI scenarios and during testing.

However, currently func pack won't run on C# in-process projects because of this check that includes ignoreDotNetCheck. The func azure functionapp publish path works correctly because ignoreDotNetCheck is set to true, but not in func pack.

Interestingly, func pack seems to work fine for C# isolated projects, because the C# check is only on WorkerRuntime.dotnet. We should also unblock func pack for C# in-process apps.

+ @mattchenderson for awareness.