Fix chaining GRS commands so they work smoothly and don't add intermediate undo steps (#2297)

Fix GRS chaining behaviour and generalise Abort to have n≠1 undos

Fixes https://discord.com/channels/731730685944922173/881073965047636018/1328281947918696458

editor/src/messages/portfolio/document/document_message.rs

@@ -165,6 +165,9 @@ pub enum DocumentMessage {
 	EndTransaction,
 	CommitTransaction,
 	AbortTransaction,
+	RepeatedAbortTransaction {
+		undo_count: usize,
+	},
 	AddTransaction,
 	ToggleLayerExpansion {
 		id: NodeId,

editor/src/messages/portfolio/document/document_message_handler.rs

@@ -1183,11 +1183,17 @@ impl MessageHandler<DocumentMessage, DocumentMessageData<'_>> for DocumentMessag
 				self.document_redo_history.clear();
 			}
 			DocumentMessage::AbortTransaction => {
+				responses.add(DocumentMessage::RepeatedAbortTransaction { undo_count: 1 });
+			}
+			DocumentMessage::RepeatedAbortTransaction { undo_count } => {
 				if self.network_interface.transaction_status() == TransactionStatus::Finished {
 					return;
 				}
 
-				self.undo(ipp, responses);
+				for _ in 0..undo_count {
+					self.undo(ipp, responses);
+				}
+
 				self.network_interface.finish_transaction();
 				responses.add(OverlaysMessage::Draw);
 			}