Merge branch 'ip6mr-no-rtnl-for-rtnl_family_ip6mr-rtnetlink'

Kuniyuki Iwashima says:

====================
ip6mr: No RTNL for RTNL_FAMILY_IP6MR rtnetlink.

This series is the IPv6 version of

  https://lore.kernel.org/netdev/20260228221800.1082070-1-kuniyu@google.com/

and removes RTNL from ip6mr rtnetlink handlers.

After this series, there are a few RTNL left in net/ipv6/ip6mr.c
and such users will be converted to per-netns RTNL in another
series.

Patch 1 extends the ipmr selftest to exercise most of the RTNL
 paths in net/ipv6/ipmr.c

Patch 2 - 6 converts RTM_GETROUTE handlers to RCU.

Patch 7 removes struct fib_dump_filter.rtnl_held.

Patch 8 use RCU for mr_table for CONFIG_IPV6_MROUTE_MULTIPLE_TABLES=n
 for ->exit_rtnl().

Patch 9 move fib_rules_unregister() to ->exit()

Patch 10 - 12 converts ->exit_batch() to ->exit_rtnl() to
 save one RTNL in cleanup_net().

Patch 13 removes unnecessary RTNL during setup_net() failure.

Patch 14 drops RTNL for MRT6_(ADD|DEL)_MFC(_PROXY)?.

Patch 15 misc clean up

v2: https://lore.kernel.org/20260410211726.1668756-1-kuniyu@google.com
v1: https://lore.kernel.org/20260407212001.2368593-1-kuniyu@google.com
====================

Link: https://patch.msgid.link/20260604224712.3209821-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>