win, fs: detect if symlink target is a directory

On Windows creating a symlink to a directory will not work unless extra
'dir' parameter is passed. This adds a check if link target is a
directory, and if so automatically use 'dir' when creating symlink.

PR-URL: https://github.com/nodejs/node/pull/23724
Refs: https://github.com/nodejs/node/pull/23691


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>