Simplify initialization of OpenFileTracker

[jasonmalinowski]

There's only two things here that could potentially need the UI thread:

1. The Running Document Table subscription, but OpenTextBufferProvider already abstracted that away.
2. The IEditorOptionsFactoryService usage, which being a MEF component shouldn't care, but even then we don't need it right away.

It's easy to clean all this up, so just do so.

[ToddGrun]

var openFileTracker = await OpenFileTracker.CreateAsync(this, ProjectSystemProjectFactory, asyncServiceProvider).ConfigureAwait(true);

Does the SwitchToMainThreadAsync call above still need to always yield since the amount of work being done is much less now?

[ToddGrun]

Oh, maybe getting the telemetry session is still potentially costly

[ToddGrun]

That's a pretty old dependency, might be worth checking whether that still needs to happen on the ui thread

[jasonmalinowski]

I'm ahead of you! #79282

[jasonmalinowski]

And @davkean confirmed the session is created really early during VS startup, so no worries about it.

[ToddGrun]

Nice! Is the yielding on the main thread switch still worthwhile then?

[jasonmalinowski]

I'm leaving it, since once this is in, I'm doing a follow-up to delete the initialize method entirely since the only remaining work would be the UIContext stuff which doesn't need the UI thread anymore either.