FoldersAPI cannot check for existing root folders

[ramo-j]

Using the FoldersAPI, I am unable to:

• Check if a root folder with a given name exists
• Get the numeric ID of a root folder given a name

Both of these could be achieved with a method similar to GetFolderID(str) -> int | None (or perhaps throws an exception like FolderNotFoundException?)

Without this, a user needs to know the non-user-friendly numeric ID, or multiple root folders with the same name will be created.

[ramo-j]

All the above also applies to subfolders as well.