Use non-batched getblock RPC

Following https://github.com/romanz/electrs/issues/373#issuecomment-785753029

src/daemon.rs

@@ -516,19 +516,6 @@ impl Daemon {
             .get_or_else(&blockhash, || self.load_blocktxids(blockhash))
     }
 
-    pub fn getblocks(&self, blockhashes: &[BlockHash]) -> Result<Vec<Block>> {
-        let params_list: Vec<Value> = blockhashes
-            .iter()
-            .map(|hash| json!([hash.to_hex(), /*verbose=*/ false]))
-            .collect();
-        let values = self.requests("getblock", &params_list)?;
-        let mut blocks = vec![];
-        for value in values {
-            blocks.push(block_from_value(value)?);
-        }
-        Ok(blocks)
-    }
-
     pub fn gettransaction(
         &self,
         txhash: &Txid,

src/index.rs

@@ -384,9 +384,13 @@ impl Index {
         let blockhashes: Vec<BlockHash> = new_headers.iter().map(|h| *h.hash()).collect();
         let batch_size = self.batch_size;
         let fetcher = spawn_thread("fetcher", move || {
-            for chunk in blockhashes.chunks(batch_size) {
+            for blockhashes_chunk in blockhashes.chunks(batch_size) {
+                let blocks = blockhashes_chunk
+                    .iter()
+                    .map(|blockhash| daemon.getblock(blockhash))
+                    .collect();
                 sender
-                    .send(daemon.getblocks(&chunk))
+                    .send(blocks)
                     .expect("failed sending blocks to be indexed");
             }
             sender