#25794 Add setting to disable or rename current project root favorite directory

Currently we automatically add a favourite directory entry to the file chooser for the project root. These look like "Shotgun Project Root". Multi-root setups have an entry for each root like this: "Shotgun Project Root (secondary)", etc. This can be quite redundant so some studios. And the name of the favourite is quite lengthy. This can make things cluttered in that pane in the file chooser.

This code adds a setting `current_project_favourite_name` allowing you to rename the menu to anything you like (in multi-root setups, the root name will still be automatically added on to the end of the name). Additionally, if you specify an empty string `''` as the value, this will disable adding the menu to the favorites pane.
ah yes. I was thinking we put it in the loop to ensure we're deleting any lingering entries that aren't there anymore but that wouldn't work anyway. Unfortunately in Nuke, unless we know the names of the favourites, we cannot delete them. So if someone decides to completely change the names they're using, they'll have to manually remove them in the UI. 

I'll make the change.