Modernize DVD package set in preparation for 14.1

Remove archivers/unzip (now in base) and emulators/linux_base-c7 (old
and unlikely to be useful without other linux packages being installed),
ports-mgmt/portmaster (now largely obsolete and discouraged in favour
of using pkg and binary packages) and x11-drivers/xf86-video-vmware
(questionably useful).

Replace devel/git with devel/git@lite (sufficient for most purposes),
and adjust the "ensure the ports exist to sanitize the list" code to
ignore the @lite part when checking that /usr/ports/devel/git exists.

Add sysutils/seatd and x11-wm/sway for wayland support.

Approved by: re (cperciva)
MFC after: 1 minute
Differential Revision: https://reviews.freebsd.org/D45278

(cherry picked from commit d31ed58b9f9360cecd9acfbd12999190edca6e56)
(cherry picked from commit 0543cdc36ac6c91dccc2f1c5ae1df42c6d4d2a1d)