ssh: switch type of matchBlocks to listOrDagOf

This switches the type of `matchBlocks` from `loaOf` to `listOrDagOf`.
The former has been deprecated in Nixpkgs. The latter allows
dependencies between entries to be expressed using the DAG functions.

tests/modules/programs/ssh/match-blocks-attrs-expected.conf

@@ -16,6 +16,9 @@ Host xyz
   RemoteForward /run/user/1000/gnupg/S.gpg-agent.extra /run/user/1000/gnupg/S.gpg-agent
   DynamicForward [localhost]:2839
 
+Host ordered
+  Port 1
+
 Host *
   ForwardAgent no
   Compression no

tests/modules/programs/ssh/match-blocks-attrs.nix

@@ -12,6 +12,8 @@ with lib;
           proxyJump = "jump-host";
         };
 
+        ordered = hm.dag.entryAfter [ "xyz" ] { port = 1; };
+
         xyz = {
           identityFile = "file";
           serverAliveInterval = 60;