Avoid accessing IVs apis off of the UI thread

[vritant24]

When the Test Explorer requests for a list of test containers from the test adapters through a property, the nodejs adapter calls IVs APIs to retrieve necessary information, but doesn't do so after switching to the UI thread which can cause deadlocks.

It is recommended that the thread should instead be switched to the UI thread using JTF.SwitchToMainThreadAsync before accessing the IVs APIs and switched off of it using await Task.Default when done,