Since not many people are using fscryptctl yet, and v1 encryption
policies have some annoying limitations which people keep running into,
and all major users of filesystem encryption have already switched to v2
by default, it's better to just drop the fscryptctl support for v1
policies and only support v2.  This keeps things much simpler going
forward, and reduces the chance that people misconfigure things.

If anyone really needs to continue to use v1-encrypted directories with
fscryptctl (despite the known limitations with key visibility and so
on), they can just use an older version of fscryptctl.