setfacl: add recursive functionality

Add a -R option to setfacl to operate recursively on directories, along
with the accompanying flags -H, -L, and -P (whose behaviour mimics
chmod).

A patch was submitted with PR 155163, but this is a new implementation
based on comments raised in the Phabricator review for that patch
(review D9096).

PR: 155163
Submitted by: Mitchell Horne <mhorne063@gmail.com>
Reviewed by: jilles
MFC after: 2 weeks
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D14934