sweep+walletrpc+lncli: report requested fee preference for pending sweeps

Previously only the fee rate used for the last sweep (the sweep bucket
average) was reported. This commit adds the request fee preference to
the report, which is used to select a bucket and the sweep tx fee rate.

lnrpc/walletrpc/walletkit.proto

@@ -191,6 +191,12 @@ message PendingSweep {
     sweep transaction of the output.
     */
     uint32 next_broadcast_height = 6 [json_name = "next_broadcast_height"];
+
+    // The requested confirmation target for this output.
+    uint32 requested_conf_target = 8 [json_name = "requested_conf_target"];
+
+    // The requested fee rate, expressed in sat/byte, for this output.
+    uint32 requested_sat_per_byte = 9 [json_name = "requested_sat_per_byte"];
 }
 
 message PendingSweepsRequest {