Add support for ESN in cryptosoft

This patch adds support for IPsec ESN (Extended Sequence Numbers) in
encrypt and authenticate mode (eg. AES-CBC and SHA256) and combined mode
(eg. AES-GCM).

For encrypt and authenticate mode the ESN is stored in separate crp_esn
buffer because the high-order 32 bits of the sequence number are
appended after the Next Header (RFC 4303).

For combined modes the high-order 32 bits of the sequence number [e.g.
RFC 4106, Chapter 5 AAD Construction] are part of crp_aad (prepared by
netipsec layer in case of ESN support enabled), therefore non visible
diff around combined modes.

Submitted by: Grzegorz Jaszczyk <jaz@semihalf.com>

Patryk Duda <pdk@semihalf.com>

Reviewed by: jhb
Differential revision: https://reviews.freebsd.org/D22364
Obtained from: Semihalf
Sponsored by: Stormshield