RFC: FilePaths2.jl

[ExpandingMan]

Hello all. I have, over the past couple of months, been extremely determined to completely solve what I consider to be an unfortunate state of affairs with S3Path from AWSS3.jl. You've probably all seen my speculative PR's having to do with adding traits to accommodate this. I have recently largely rewritten AbstractTrees.jl partially in service of this goal.

I've ultimately given the situation a lot more thought and have come up with FilePaths2.jl.

The package is currently deliberately incomplete as I would like to solicit opinions. FilePathsBase.jl could be overhauled based on my approach in FilePaths2.jl. I'd be glad to do that, but obviously I do not know what the maintainers would think of that. My current repo of FilePaths2.jl is meant as an example of what I intend to do, please see the README for a more careful exposition of what I did and why.

Would like to hear opinions about whether the maintainers would be receptive to moving AWSS3.jl to be based on this approach, whether that would be the result of changing FilePathsBase or a new package. (Cross posting here)