Make necessary changes for 23.05

- Explicitly enable fish
- No longer use OpenSSL 1.1 for BURP (decryption now seems to work fine
  with current OpenSSL)
- Move sshd settings to `settings`

overlays/burp.nix

@@ -11,7 +11,6 @@
                     hash = "sha256-/vYon0XUIuMAaaaRNehzMspKMHWp0tJm8JubRt1KmZU=";
                 };
                 configureFlags = [ "--sysconfdir=/var/lib/burp" ];
-                buildInputs = with super; [ librsync ncurses openssl_1_1 zlib uthash ];
                 patches = [];
             }));
         })