lightningd: add short_channel_id option to listpeerchannels.

Requested-by: @whitslack
Closes: https://github.com/ElementsProject/lightning/issues/8233
Changelog-Added: JSON-RPC: `listpeerchannels` now has a `short_channel_id` parameter for just listing a specific channel.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

doc/schemas/listpeerchannels.json

@@ -21,6 +21,13 @@
         "description": [
           "If supplied, limits the channels to just the peer with the given ID, if it exists."
         ]
+      },
+      "short_channel_id": {
+        "added": "v25.05",
+        "type": "short_channel_id",
+        "description": [
+          "If supplied, limits the channels to just this short_channel_id (or local alias), if it exists.  Cannot be used with 'id'."
+        ]
       }
     }
   },