state: make Response::Tip return (height, hash)

zebra-consensus/src/chain.rs

@@ -134,7 +134,7 @@ where
         zs::Response::Tip(tip) => tip,
         _ => unreachable!("wrong response to Request::Tip"),
     };
-    let tip = if let Some(hash) = tip_hash {
+    let tip = if let Some((_height, hash)) = tip_hash {
         match state_service
             .ready_and()
             .await

zebra-state/src/response.rs

@@ -17,10 +17,10 @@ pub enum Response {
     Committed(block::Hash),
 
     /// Response to [`Request::Depth`] with the depth of the specified block.
-    Depth(Option<block::Height>),
+    Depth(Option<u32>),
 
     /// Response to [`Request::Tip`] with the current best chain tip.
-    Tip(Option<block::Hash>),
+    Tip(Option<(block::Height, block::Hash)>),
 
     /// Response to [`Request::BlockLocator`] with a block locator object.
     BlockLocator(Vec<block::Hash>),