emulators/i386-wine-devel: Remove port.

This port and its pre-built binaries have not been updated lately and
emulators/wine-devel is now providing i386 support on amd64, so remove
i386-wine-devel.

Adjust CONFLICTS_INSTALL on related ports and simplify (and update both
user and developer documentation in wine-devel).

Approved by: maintainer (= submitter)
PR: 259589
Differential Revision: https://reviews.freebsd.org/D32322