perf: pre-allocate all known length arrays to avoid re-scaling (#5029)

Co-authored-by: Kevin Wan <wanjunfeng@gmail.com>

core/stores/redis/redis.go

@@ -1944,7 +1944,7 @@ func (s *Redis) ZaddsCtx(ctx context.Context, key string, ps ...Pair) (int64, er
 		return 0, err
 	}
 
-	var zs []red.Z
+	zs := make([]red.Z, 0, len(ps))
 	for _, p := range ps {
 		z := red.Z{Score: float64(p.Score), Member: p.Key}
 		zs = append(zs, z)