Rename Message::Inventory -> Message::Inv

I don't feel super strongly about this change, so I'm happy to drop it,
but it makes the parsing match statements line up nicely and aligns
naming with the naming used in Bitcoin.

zebra-network/src/protocol/codec.rs

@@ -126,7 +126,7 @@ impl Encoder for Codec {
             GetBlocks { .. } => b"getblocks\0\0\0",
             Headers { .. } => b"headers\0\0\0\0\0",
             GetHeaders { .. } => b"getheaders\0\0",
-            Inventory { .. } => b"inv\0\0\0\0\0\0\0\0\0", // XXX Inventory -> Inv ?
+            Inv { .. } => b"inv\0\0\0\0\0\0\0\0\0",
             GetData { .. } => b"getdata\0\0\0\0\0",
             NotFound { .. } => b"notfound\0\0\0\0",
             Tx { .. } => b"tx\0\0\0\0\0\0\0\0\0\0",
@@ -422,7 +422,7 @@ impl Codec {
             hashes.push(InventoryHash::zcash_deserialize(&mut reader)?);
         }
 
-        Ok(Message::Inventory(hashes))
+        Ok(Message::Inv(hashes))
     }
 
     fn read_getdata<R: Read>(&self, mut _reader: R) -> Result<Message, Error> {

zebra-network/src/protocol/message.rs

@@ -163,7 +163,7 @@ pub enum Message {
     // XXX the bitcoin reference above suggests this can be 1.8 MB in bitcoin -- maybe
     // larger in Zcash, since Zcash objects could be bigger (?) -- does this tilt towards
     // having serialization be async?
-    Inventory(Vec<InventoryHash>),
+    Inv(Vec<InventoryHash>),
 
     /// A `getdata` message.
     ///