LU-12275 sec: add llcrypt as file encryption library

LU-12275 sec: add llcrypt as file encryption library

Include fscrypt sources from Linux 5.4 into libcfs kernel module.
All fscrypt_ prefixes have been replaced with llcrypt_ to avoid
collision. For the exact transformations carried out, please see
script contrib/scripts/fscrypt_inclusion.sh, and patches under
contrib/scripts/crypto_patches/.

This llcrypt library will be built if kernel provides minimum
encryption support, ie IS_ENCRYPTED and S_ENCRYPTED.
If kernel provides support for encryption policies v2 (included in
Linux 5.4), then llcrypt library will not be built, and in-kernel
fscrypt will be used instead.

To be independent as much as possible from the kernel, llcrypt relies
on a new 'lsi_cop' field added to struct lustre_sb_info, to point to
struct llcrypt_operations, and makes use of the new 'lsi_master_keys'
field to store file system keys. llcrypt also uses i_private field on
struct inode to store file-specific enryption info.

Test-Parameters: trivial
Test-Parameters: clientdistro=ubuntu1804 testgroup=review-ldiskfs
Test-Parameters: clientdistro=el8.1 testgroup=review-ldiskfs
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ide2431b0c3381214aed2e54dd3084132e9545ca8
Reviewed-on: https://review.whamcloud.com/38127
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>