LU-10391 libcfs: add large-nid string conversion functions.

LU-10391 libcfs: add large-nid string conversion functions.

The user-space libcfs now has functions to convert between strings and
large nids.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I554e2da0c3d56397ebe60fc84fad28fec6704a18
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50092
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>