Host key checking is lazy

[spoutn1k]

Hello,

I am facing an issue when connecting with russh to a host I previously connected to with the system ssh.

The system ssh will leave the known host file in this state upon first connection:

host ssh-ed25519 AAAAC3NzaC1...
host ssh-rsa AAAAB3NzaC1...
host ecdsa-sha2-nistp256 AAAAE2VjZH...

Turns out check_known_hosts does not like this very much and will error out with russh_keys::Error::KeyChanged if the ecdsa-sha2-nistp256 key is not first. I imagine it does not look past the first hostname match, yet this is not how OpenSSH_9.7p1, OpenSSL 3.3.1 4 Jun 2024 leaves the keys ...

Upon confirmation that this is not intended behaviour I'll submit a PR. Thanks !