yes: Completely overengineer

If we're going to overengineer this, we may as well go all the way.

• If multiple arguments are given, concatenate them into a space- separated list like GNU coreutils does.

• When duplicating the expletive, do so exponentially.

• Most importantly, don't modify the memory that argv points to.

MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: kevans, allanjude
Differential Revision: https://reviews.freebsd.org/D55617

(cherry picked from commit cf74b63d61b49db848ecc20b87e7ee5f16671320)

yes: Add missing header

This is a no-op on FreeBSD due to namespace pollution.

MFC after: 1 week
Sponsored by: Klara, Inc.
Fixes: cf74b63d61b4 ("yes: Completely overengineer")

(cherry picked from commit ba7439f0a9604b15bfef8084816f34d55eb6bdf2)