LU-11971 utils: add 'lfs find -crtime' alias

LU-11971 utils: add 'lfs find -crtime' alias

Add "-crtime" as an alias for "-btime" since this field is
also commonly called file creation time.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Id136561ec37756caf29e20e8a548171496be0e72
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58398
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>