Add IWorkspaceProjectContextFactory F# wappers

[tmat]

External access for IWorkspaceProjectContextFactory

Equivalent of https://github.com/dotnet/fsharp/blob/9620686d297e5c4990daca6a707f2bd7f067c028/vsintegration/src/FSharp.Editor/LanguageService/SingleFileWorkspaceMap.fs#L17-L139

Corresponding F# follow up change: dotnet/fsharp#13514

[tmat]

@jasonmalinowski

[jasonmalinowski]

One thing to track as a part of this: once F# is moved to it's own interface then we can move this:

roslyn/src/VisualStudio/Core/Impl/ProjectSystem/CPS/CPSProjectFactory.cs

Lines 83 to 96 in 5f135a0

	if (languageName == LanguageNames.FSharp)
	{
	await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
	var shell = await _serviceProvider.GetServiceAsync<SVsShell, IVsShell7>(_threadingContext.JoinableTaskFactory).ConfigureAwait(true);
	// Force the F# package to load; this is necessary because the F# package listens to WorkspaceChanged to
	// set up some items, and the F# project system doesn't guarantee that the F# package has been loaded itself
	// so we're caught in the middle doing this.
	var packageId = Guids.FSharpPackageId;
	await shell.LoadPackageAsync(ref packageId);
	await TaskScheduler.Default;
	}

into here so that way that's not confusing people for it being there.