fix: set IdentityFile defaults to match man page

The existing default IdentityFile list was incomplete and out of order.
This updates it to match the defaults listed here:
https://man7.org/linux/man-pages/man5/ssh_config.5.html

validators.go

@@ -183,10 +183,12 @@ var defaults = map[string]string{
 
 // these identities are used for SSH protocol 2
 var defaultProtocol2Identities = []string{
-	"~/.ssh/id_dsa",
-	"~/.ssh/id_ecdsa",
-	"~/.ssh/id_ed25519",
 	"~/.ssh/id_rsa",
+	"~/.ssh/id_ecdsa",
+	"~/.ssh/id_ecdsa_sk",
+	"~/.ssh/id_ed25519",
+	"~/.ssh/id_ed25519_sk",
+	"~/.ssh/id_dsa",
 }
 
 // these directives support multiple items that can be collected