USE_FOLDERS: add a new property to autogenerate target folders based on project folder structure
When using generators that use folders and enabling the USE_FOLDERS property it is up to the project to set folders for every target they create (either by setting it per target or using CMAKE_FOLDER). It would be nice to have another property, or extend USE_FOLDERS, to automatically generate a value for this folder property based on where targets are created in a project's folder tree.
I'm opening this in response to Brad's request here: !7378 (comment 1205919)
And here's an initial attempt at solving this: !7378 (closed)