WIP: [PoC] Alternative Step 2 of #62214: Includes logic to update namespaces storage statistics

What does this MR do?

This is a rebased version of @mayra-cabrera works in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29570 and gitlab-org/gitlab-ce!28996

My only addition is on commit 11047846

This is an attempt to achieve gitlab-org/gitlab-ce#62214 without adding a new column on namespaces table that tracks the root namespace and calculate the statistics based on this column (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/28996#note_178311781)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team