vendor: move vendored sources in-tree

This should make it easier to see changes instead of just a blob

vendor/github.com/redis/go-redis/v9/internal/internal.go

@@ -0,0 +1,29 @@
+package internal
+
+import (
+	"time"
+
+	"github.com/redis/go-redis/v9/internal/rand"
+)
+
+func RetryBackoff(retry int, minBackoff, maxBackoff time.Duration) time.Duration {
+	if retry < 0 {
+		panic("not reached")
+	}
+	if minBackoff == 0 {
+		return 0
+	}
+
+	d := minBackoff << uint(retry)
+	if d < minBackoff {
+		return maxBackoff
+	}
+
+	d = minBackoff + time.Duration(rand.Int63n(int64(d)))
+
+	if d > maxBackoff || d < minBackoff {
+		d = maxBackoff
+	}
+
+	return d
+}