Merge 'perf/throughput/turso: Don't interleave concurrent transactions in on…' from Pekka Enberg

…e connection
With BEGIN CONCURRENT, we cannot use the same connection all the time
because there's no way for the transaction manager to know which
transaction belongs to what "session" -- they're all individual
statements executed in the context of the one connection.
Fixes #3093

Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>

Closes #3094

perf/throughput/turso/src/main.rs

@@ -150,8 +150,6 @@ async fn worker_thread(
     mode: TransactionMode,
     think_ms: u64,
 ) -> Result<u64> {
-    let conn = db.connect()?;
-
     start_barrier.wait();
 
     let start_time = Instant::now();
@@ -160,7 +158,7 @@ async fn worker_thread(
     let mut tx_futs = vec![];
 
     for iteration in 0..iterations {
-        let conn = conn.clone();
+        let conn = db.connect()?;
         let total_inserts = Arc::clone(&total_inserts);
         let tx_fut = async move {
             let mut stmt = conn