fs: align symlink parameter names with std

[florian-g2]

Motivation

Using src and dst as parameter names in the context of symlinks is confusing, especially in their order.

I usually think from left to right: a symlink points to a target.
So I assumed that src would point to dst, but that isn’t the case here.

Solution

Align to the standard library and use original and link as the parameter names.

[maminrayej]

LGTM. But for consistency, please also rename the parameters for hard_link as well.