inetd: Add examples from manual page and other sources

The manual page lists a bunch of examples, some of which already exist
in this file. Since it's both easier to remember when all examples are
listed in the same location, move examples so they get installed into
/etc/inetd.conf

This also means users won't have to copy-paste, but can simply
uncomment one or more services to use them.

As such, it also becomes necessary to remove the examples from the
manual page, so instead add a note explaining where the previous
examples as well as others may be found.
Cross-references, including to ports, have also been added where
applicable.

The rsync example has lived in the bug tracker for too long,
considering how useful it can situationally be, for example when
backup jobs on client devices are run through periodic(8) weekly.

The microsoft-ds entry is necessary for Windows 10 compatibility
(this can be confirmed with packet capturing, as it is not readily
documented at time of writing).

While here, remove two examples for which compatible daemons could not
be found in ports.

Submitted by: David Yeske <dyeske at gmail.com> (in part, prev ver)
PR: 122037
Reviewed by: kevans, brueffer, lwhsu, yuripv
Differential Revision: https://reviews.freebsd.org/D28882