Directory.Move: Undocumented exception

Repro:

1. Create a directory `C:\temp\A`. Make sure that the directory `C:\temp\B` **does not exist.**
2. Execute `Directory.Move(@"C:\temp\A", @"C:\temp\B\C");`

Note that you get the following exception: `System.IO.DirectoryNotFoundException: Could not find a part of the path.`

However, the [documentation of Directory.Move](https://docs.microsoft.com/en-us/dotnet/api/system.io.directory.move?view=netframework-4.8) states that a `DirectoryNotFoundException` is only thrown in the following case:

> The path specified by sourceDirName is invalid (for example, it is on an unmapped drive).

In this case, the path specified by sourceDirName is *not* invalid.

Suggested fix:

1. Find out under which circumstances `Directory.Move` can throw a `DirectoryNotFoundException` (in the example above, it's the fact that the parent of the path specified by `destDirName` does not exist, but there might be others as well).
2. Update the documentation to list all the cases.