make_benchmark_block_proposals now returns BlockProposals (linera-io#…

…3264)

## Motivation

This `RpcMessage` type is needed only when calling `mass_broadcast`, and it makes the code a bit more awkward because you have to check if it's a block proposal, when it'll always be

## Proposal

Return the actual `BlockProposal`s instead, and only convert them when needed.

## Test Plan

CI + ran locally

## Release Plan

- Nothing to do / These changes follow the usual release cycle.

linera-client/src/client_context.rs

@@ -843,7 +843,7 @@ where
         key_pairs: &HashMap<ChainId, KeyPair>,
         transactions_per_block: usize,
         fungible_application_id: Option<ApplicationId>,
-    ) -> Vec<RpcMessage> {
+    ) -> Vec<BlockProposal> {
         let mut proposals = Vec::new();
         let mut previous_chain_id = *key_pairs
             .iter()
@@ -887,7 +887,7 @@ where
                 block.clone(),
                 key_pair,
             );
-            proposals.push(RpcMessage::BlockProposal(Box::new(proposal)));
+            proposals.push(proposal);
             previous_chain_id = chain.chain_id;
         }
         proposals

linera-service/src/linera/main.rs

@@ -809,16 +809,24 @@ impl Runnable for Job {
                 let num_proposal = proposals.len();
                 let mut values = HashMap::new();
 
-                for rpc_msg in &proposals {
-                    if let RpcMessage::BlockProposal(proposal) = rpc_msg {
-                        let executed_block = context
-                            .stage_block_execution(proposal.content.block.clone(), None)
-                            .await?;
-                        let value = Hashed::new(ConfirmedBlock::new(executed_block));
-                        values.insert(value.hash(), value);
-                    }
+                let start = Instant::now();
+                for proposal in &proposals {
+                    let executed_block = context
+                        .stage_block_execution(proposal.content.block.clone(), None)
+                        .await?;
+                    let value = Hashed::new(ConfirmedBlock::new(executed_block));
+                    values.insert(value.hash(), value);
                 }
+                info!(
+                    "Staged {} block proposals in {} ms",
+                    num_proposal,
+                    start.elapsed().as_millis()
+                );
 
+                let proposals = proposals
+                    .into_iter()
+                    .map(|proposal| RpcMessage::BlockProposal(Box::new(proposal)))
+                    .collect::<Vec<_>>();
                 let responses = context.mass_broadcast("block proposals", proposals).await;
                 let votes = responses
                     .into_iter()