Define a default storage limit for package feature

Problem to solve

When we start counting the amount of storage space uploaded packages take with https://gitlab.com/gitlab-org/gitlab-ce/issues/59232, we will need to define a default storage limit.

Intended users

All users who use Package feature.

Further details

Each project can have a certain soft limit for any of the Maven/npm/other types of uploads that end up in Package view.

Proposal

Instead of defining the amount specifically for package feature, I propose we define two generic limits on the group level that each of package, container registry, etc. will count against.

This means that if we set a storage limit, of for example 10GB, on the group level for the whole object storage group of items, users can decide if they want to use whole 10GB for package or something else.

We should be able to define two limits: a soft limit and a hard limit. An instance may set one, both, or none.

This issue defines the limit on the backend, but does not call for any treatment in the UI once the limit is reached. Those UX and frontend changes are covered in https://gitlab.com/gitlab-org/gitlab-ce/issues/30421.

Permissions and Security

Once the default limit is reached, at first iteration we should show a group notice that the group storage is used up. At this iteration we do not need to think about enforcing the storage limits

Links / references

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/59232