Host wide ICMP ratelimiter should be per netns, to provide better isolation.

Following patch in this series makes the sysctl per netns.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20240829144641.3880376-3-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>