win,fs: use namespaced path in absolute symlinks

Use the namespaced (with the \\?\ prefix) paths for symlink targets when
the path is absolute. This allows creation of symlinks to files with
long filenames.

Fixes: https://github.com/nodejs/node/issues/27795

PR-URL: https://github.com/nodejs/node/pull/33351


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>