Write `get-file` and commands to get the list of blocks from another node

Description

This closes #1 (closed) by providing an API that allows to get a file with just its hash

Detailed list of changes

• add get_file, get_blocks_info_from and other things related to managing the filesystem
• add new commands to nu API
• remove DragoonBehaviour as it was not useful
• add two new tests for get_file and change the already existing test to use the new API

Note

The get_file is still very rough, the error management needs to be handled better to take into a lot more cases of failure

src/dragoon_network.rs

@@ -126,7 +126,7 @@ where
     file_dir: PathBuf,
     pending_start_providing: HashMap<kad::QueryId, Sender<()>>,
     pending_get_providers: HashMap<kad::QueryId, Sender<Vec<PeerId>>>,
-    pending_request_file: HashMap<OutboundRequestId, Sender<Vec<u8>>>,
+    pending_request_block: HashMap<OutboundRequestId, Sender<Vec<u8>>>,
 }
 
 impl<F, G> DragoonNetwork<F, G>
@@ -147,7 +147,7 @@ where
             file_dir: Self::create_block_dir(peer_id, replace).unwrap(),
             pending_start_providing: Default::default(),
             pending_get_providers: Default::default(),
-            pending_request_file: Default::default(),
+            pending_request_block: Default::default(),
         }
     }
 
@@ -314,7 +314,7 @@ where
                     request_id,
                     response,
                 } => {
-                    if let Some(sender) = self.pending_request_file.remove(&request_id) {
+                    if let Some(sender) = self.pending_request_block.remove(&request_id) {
                         if sender.send(Ok(response.0)).is_err() {
                             error!("Couldn't send the result of the message response operation of id {}", request_id);
                         }
@@ -494,7 +494,7 @@ where
                         block_hash,
                     },
                 );
-                self.pending_request_file.insert(request_id, sender);
+                self.pending_request_block.insert(request_id, sender);
             }
             DragoonCommand::DragoonPeers { sender } => {
                 if sender