Split migrations folder (#21549)

There are too many files in `models/migrations` folder so that I split
them into sub folders.

models/migrations/v1_11/v116.go

@@ -0,0 +1,33 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package v1_11 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+func ExtendTrackedTimes(x *xorm.Engine) error {
+	type TrackedTime struct {
+		Time    int64 `xorm:"NOT NULL"`
+		Deleted bool  `xorm:"NOT NULL DEFAULT false"`
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if _, err := sess.Exec("DELETE FROM tracked_time WHERE time IS NULL"); err != nil {
+		return err
+	}
+
+	if err := sess.Sync2(new(TrackedTime)); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}