Add implmentation for fwide posix function.

This function is used to set the orientation of a stream to either
byte-oriented or wchar-oriented.

More info on this function is here:
https://man7.org/linux/man-pages/man3/fwide.3p.html



This implementation only impmlemnts the manual switching and does
not yet guard against using a byte-oriented stream with wchar
functions and vice versa. Those step will come in additional
commits.

Signed-off-by: Wren Turkal <wt@penguintechs.org>