Replace pipeline quota with usage quota

What does this MR do?

Follow-up from !28387 (merged). This removes the feature flag and the old code and rolls out usage quota for user namespaces. Previously we had "Pipeline Quota" which now gets replaced by "Usage Quotas", which not only shows the pipeline stats but also storage usage stats.

The feature flag is already set for gitlab.com and pages can be seen here https://gitlab.com/profile/usage_quotas

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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

Closes #213425 (closed)