LU-17263 utils: 'lfs find -blocks' to use 512-byte units

LU-17263 utils: 'lfs find -blocks' to use 512-byte units

Change the default units for 'lfs find -blocks' from 1KiB blocks
to 512-byte blocks to better match the behavior of find(1).  This
also matches what "-printf %b" will print.

Change llapi_parse_size() to accept a 'c' argument to specify
characters, and accept a "B" or "iB" suffix if provided.

Fixes: c043f46025 ("LU-10705 utils: add "lfs find --blocks"")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: If8345f15bf53912501cadc0fa7f981a9f787b767
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52993
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>