LU-16760 utils: support 'lfs find --attrs' and '-printf %La'

LU-16760 utils: support 'lfs find --attrs' and '-printf %La'

Add support to "lfs find" to filter on file attribute flags, with the
syntax "[!] --attrs=[^]ATTR[,...]".
Add support to "lfs find" to print file attribute flags with
"-printf %La".

Lustre-change: https://review.whamcloud.com/51562
Lustre-commit: f0ab3ac6d6e31472c20ef538b799b96a512087f7

Add sanity-sec test_65 for Encrypted and Immutable flags.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I5e5cfe5c8c8cbed8bb79f3ad6d8116347ecfe6ac
Reviewed-by: Zhenyu Xu <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52067
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>