LU-9680 lnet: collect data about routes by using Netlink

LU-9680 lnet: collect data about routes by using Netlink

Migrate the LNet route API to use the Netlink API for
the case of collecting data about routes. This change also
allows large NID support for IPv6. Support for adding and
deleting routes with Netlink will be done in an follow on
patch.

Test-Parameters: trivial testlist=sanity-lnet
Change-Id: Ic8a9eb1f2571b14049a385698594849a585878ca
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49839
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>