Cache INSERT statement in receive_imf

It reduces iteration time by ~8% in message reception benchmarks
ran by `cargo criterion --bench receive_emails`.

src/receive_imf.rs

@@ -1149,7 +1149,10 @@ async fn add_parts(
         // also change `MsgId::trash()` and `delete_expired_messages()`
         let trash = chat_id.is_trash() || (is_location_kml && msg.is_empty());
 
-        let row_id = context.sql.insert(
+        let row_id = context
+            .sql
+            .call(|conn| {
+                let mut stmt = conn.prepare_cached(
             r#"
 INSERT INTO msgs
   (
@@ -1179,8 +1182,8 @@ SET rfc724_mid=excluded.rfc724_mid, chat_id=excluded.chat_id,
     bytes=excluded.bytes, mime_headers=excluded.mime_headers, mime_in_reply_to=excluded.mime_in_reply_to,
     mime_references=excluded.mime_references, mime_modified=excluded.mime_modified, error=excluded.error, ephemeral_timer=excluded.ephemeral_timer,
     ephemeral_timestamp=excluded.ephemeral_timestamp, download_state=excluded.download_state, hop_info=excluded.hop_info
-"#,
-            paramsv![
+"#)?;
+                stmt.execute(params![
                     replace_msg_id,
                     rfc724_mid,
                     if trash { DC_CHAT_ID_TRASH } else { chat_id },
@@ -1219,7 +1222,11 @@ SET rfc724_mid=excluded.rfc724_mid, chat_id=excluded.chat_id,
                         DownloadState::Done
                     },
                     mime_parser.hop_info
-        ]).await?;
+                ])?;
+                let row_id = conn.last_insert_rowid();
+                Ok(row_id)
+            })
+            .await?;
 
         // We only replace placeholder with a first part,
         // afterwards insert additional parts.