Override actual_size_limit of group and namespace

What does this MR do and why?

With this issue https://jihulab.com/gitlab-cn/gitlab/-/issues/625

Follow this plan https://gitlab.com/gitlab-org/gitlab/-/merge_requests/83258#note_892237125, Override actual_size_limit method of namespace and group

Here are some introductions https://jihulab.com/gitlab-cn/gitlab/-/issues/625#note_496251

Upstream MR https://gitlab.com/gitlab-org/gitlab/-/merge_requests/83819

在 PlanLimits 表中添加 repository_size 字段用来表示每个 plan 的仓库大小限制，默认为 0，意为不启用，为 disabled 状态。然后覆写group 和 namespace 的 actual_size_limit 方法，如果是 JH 的 SAAS 环境，那么就直接读取该 namespace 或者 group 的plan 的 plan_limits 的 repository_size ，如果 repository_size 值为0， 则使用原本的方法，如果不为 0 ，使用 plan_limits 的repository_size

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Upstream related MR

Migration ( Add repository_size to plan_limits table ) https://gitlab.com/gitlab-org/gitlab/-/merge_requests/83819