Reduce integration test overhead (#32475)

In profiling integration tests, I found a couple places where per-test
overhead could be reduced:

* Avoiding disk IO by synchronizing instead of deleting & copying test
Git repository data. This saves ~100ms per test on my machine
* When flushing queues in `PrintCurrentTest`, invoke `FlushWithContext`
in a parallel.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/indexer/code/indexer_test.go

@@ -21,6 +21,7 @@ import (
 	_ "code.gitea.io/gitea/models/activities"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	_ "github.com/mattn/go-sqlite3"
 )
@@ -284,15 +285,11 @@ func TestBleveIndexAndSearch(t *testing.T) {
 	dir := t.TempDir()
 
 	idx := bleve.NewIndexer(dir)
-	_, err := idx.Init(context.Background())
-	if err != nil {
-		if idx != nil {
-			idx.Close()
-		}
-		assert.FailNow(t, "Unable to create bleve indexer Error: %v", err)
-	}
 	defer idx.Close()
 
+	_, err := idx.Init(context.Background())
+	require.NoError(t, err)
+
 	testIndexer("beleve", t, idx)
 }