fs: improve error performance of `fchownSync`
Credit to @CanadaHonk for the benchmark using file descriptors.
fs/bench-fchownSync.js n=1000 type='existing' -4.45 % ±10.42% ±13.91% ±18.21%
fs/bench-fchownSync.js n=1000 type='non-existing' *** 107.40 % ±5.36% ±7.19% ±9.48%