Explicit support for exotic paths on Windows

There are a plethora of various interesting types on Windows, including but not limited to:
- local device paths (`\\.\…`)
- root local device paths (`\\?\…`)

Read [the comprehensive guide on the paths](https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html) to learn more.

TruePath should at least support parsing and manipulating these. We should also decide what to do about path canonicalization: should we consider `new AbsolutePath("C:\Foo")` to be equal to `new AbsolutePath("\\?\C:\Foo")`? Should we trim the `\\?\` part on parsing, and automatically add it back on path quoting if requested? These are for now open questions.

I am looking for a discussion on how these are used in reality, so that we can decide on what to do with them properly.