lnrpc: add median_channel_size to NetworkInfo

lnrpc/rpc.proto

@@ -1738,6 +1738,7 @@ message NetworkInfo {
     double avg_channel_size = 7 [json_name = "avg_channel_size"];
     int64 min_channel_size = 8 [json_name = "min_channel_size"];
     int64 max_channel_size = 9 [json_name = "max_channel_size"];
+    int64 median_channel_size_sat = 10 [json_name = "median_channel_size_sat"];
 
     // TODO(roasbeef): fee rate info, expiry
     //  * also additional RPC for tracking fee info once in

lnrpc/rpc.swagger.json

@@ -2400,6 +2400,10 @@
         "max_channel_size": {
           "type": "string",
           "format": "int64"
+        },
+        "median_channel_size_sat": {
+          "type": "string",
+          "format": "int64"
         }
       }
     },