Add Storage Admin Control Columns to Plan Limits Table

What does this MR do and why?

Adds the following columns to the plan_limits table:

• enforcement_limit (integer)
• notification_limit (integer)
• dashboard_limit_enabled_at (datetime with zone)

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/385721

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.