fs: check for symlink support in fs-promises test

Attempting to make symlinks as a non-administrator user in Windows
causes a permission error. We need to update test-fs-promises to avoid
making symlinks if the platform does not support it.

PR-URL: https://github.com/nodejs/node/pull/19018


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>