icmp: increase net.ipv4.icmp_msgs_{per_sec,burst}

These sysctls were added in 4cdf507d5452 ("icmp: add a global rate
limitation") and their default values might be too small.

Some network tools send probes to closed UDP ports from many hosts
to estimate proportion of packet drops on a particular target.

This patch sets both sysctls to 10000.

Note the per-peer rate-limit (as described in RFC 4443 2.4 (f))
intent is still enforced.

This also increases security, see b38e7819cae9
("icmp: randomize the global rate limiter") for reference.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260223161742.929830-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>