Add support for KTLS receive for TLS 1.1-1.2 on FreeBSD.

Add support for KTLS receive for TLS 1.1-1.2 on FreeBSD.

Similar to KTLS receive for Linux, KTLS receive for FreeBSD is enabled
by passing a session key to the kernel via a new socket option.  Once
KTLS receive is enabled on a socket, the socket returns records via
recvmsg().  A control message attached to each record supplies the
original TLS header, and the decrypted plaintext is returned in the
data buffer passed to recvmsg().

To support the case that the userland buffer may already contain
pending encrypted records (which is already handled by Linux's KTLS
receive), the socket option structure for FreeBSD has been extended to
include the initial sequence number.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12111)