Fix issues with active document on other features

When I open a new document, this assertion https://github.com/fsprojects/VisualFSharpPowerTools/blob/f4714a54d08ebeaaf8c9f43206cda219efbea579/src/FSharpVSPowerTools.Logic/ProjectFactory.fs#L135-L136 fails for all smart tags features. `GetActiveDocument` is incorrect for the first moment we check for it.

To ensure ActiveDocument, we use file paths to do sanity check. It's an intrusive change, but I don't know how to limit its scope.