Deprication of mkpath(x) to makedir(x, recursive=true) does not work if a directory called x already exists

[oxinabox]

There are 2 differences between mkdir and mkpath

1. mkpath recursively creates directories
2. mkpath does nothing if the directory already exists, where as mkdir throws an error.

The deprecation currently only works for case 1.

[oxinabox]

Can this be moved to FilePathsBase.jl?

[rofinn]

NOTE: That's what the keyword argument exist_ok should be for. I'm starting to be convinced that we should support the exact same API as base in FilePathsBase to minimize confusion and increase the likelihood that it could become a stdlib.