Add support for IPsec ESN and pass relevant information to crypto layer

Implement support for including IPsec ESN (Extended Sequence Number) to
both encrypt and authenticate mode (eg. AES-CBC and SHA256) and combined
mode (eg. AES-GCM). Both ESP and AH protocols are updated. Additionally
pass relevant information about ESN to crypto layer.

For the ETA 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 the AEAD modes the high-order 32 bits of the sequence number
[e.g. RFC 4106, Chapter 5 AAD Construction] are included as part of
crp_aad (SPI + ESN (32 high order bits) + Seq nr (32 low order bits)).

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

Patryk Duda <pdk@semihalf.com>

Reviewed by: jhb, gnn
Differential revision: https://reviews.freebsd.org/D22369
Obtained from: Semihalf
Sponsored by: Stormshield