lnrpc: add fee rate and local close bool to PendingUpdate

This'll allow us to notify the caller each time a new coop close
transaction with a higher fee rate is signed.

lnrpc/lightning.proto

@@ -2167,6 +2167,8 @@ message CloseStatusUpdate {
 message PendingUpdate {
     bytes txid = 1;
     uint32 output_index = 2;
+    int64 fee_per_vbyte = 3;
+    bool local_close_tx = 4;
 }
 
 message InstantUpdate {