* Parse and export newly-added NL_RTA_WEIGHT attribute, providing path
weight for a non-multipath route. This fixes a number of tests in
sys/net/routing which rely on this data.
* Remove handling of NL_RTA_KNH_ID in multipath routes, as it is
not provided.
* Improve kernel/user nexthop index export. As a result,
for multipath routes:
* nhg-kidx attribute represents kernel nhg index (always provided)
* nhg-uidx attribute represents user-provided nhg index (if set)
for non-multipath routes:
* nhop-kidx attribute represents kernel nhop index (always provided)
* nhop-udx attribute represents user-provided nexthop index (if set)