Update the combined banner when exceeding both storage and user limits

What does this MR do and why?

This implements https://gitlab.com/gitlab-org/gitlab/-/issues/416794 where we make some updates to the banner for namespaces over user and storage limits:

• Swap the buttons
• Adjust the copy
• Amend the FAQ link

Screenshots or screen recordings

Group Owners

Before	After

non-Owners members

Minor addition of the word Free in the first phrase.

Before	After

How to set up and validate locally

Setting this up is a bit cumbersome given the dozens of possible states. Here's a list of steps:

1. Make sure these FFs are disabled: Feature.disable(:free_user_cap) and Feature.disable(:free_user_cap_new_namespaces)
2. Make sure free user cap dashboard is disabled: ::Gitlab::CurrentSettings.update(dashboard_limit_enabled: false)
3. Make sure this other setting is disabled: ::Gitlab::CurrentSettings.update(dashboard_limit_new_namespace_creation_enforcement_date: nil)
4. Make sure FF for storage check is disabled: Feature.disable(:free_user_cap_without_storage_check)
5. Create a new group, take note of its ID, e.g.: 88
6. Add 6+ members to that group
7. Enable Free user cap notification FF: Feature.enable(:preview_free_user_cap)
8. Set UserCap Dashboard limit: ::Gitlab::CurrentSettings.update(dashboard_limit_enabled: true, dashboard_limit: 5)
   1. You should see a banner saying something about Your top-level group will move to a read-only state soon, a.k.a the UserCap pre-enforcement banner
   Screenshot

   
9. Now with your Group (g = Group.find(88) where 88 is your group ID from step 2)
   1. Set Storage Dashboard limit: g.actual_plan.actual_limits.update(storage_size_limit: 5 * 1024) This means 5 GB
   2. Set pre-enforcement notification limit, like 6 GB: g.actual_limits.update(notification_limit: 6 * 1024)
      1. ⚠️ Important: notification_limit should be higher than storage_size_limit. There's no validation in the backend though, discussion: !124075 (comment 1439722242)
   3. Set used storage over the notification limit: g.root_storage_statistics.update(storage_size: 7.gigabytes)
      1. If you get an error, try creating the record like so Namespace::RootStorageStatistics.new(namespace: g, storage_size: 7.gigabytes).save!
10. Make sure pre-enforcement FF is enabled: Feature.enable(:namespace_storage_limit_show_preenforcement_banner)
11. Turn on automatic purchased storage allocation: ::Gitlab::CurrentSettings.update(automatic_purchased_storage_allocation: true)
12. Clear the cache: rails cache:clear
13. You should now see a banner saying something about A namespace storage limit will soon be enforced for the namespace, a.k.a the Storage pre-enforcement banner
    Screenshot

    
14. Now enabling the combined banner is possible:
    1. Via free_user_cap by simply enabling Feature.enable(:free_user_cap), or...
    2. Via free_user_cap_new_namespaces:
       1. Feature.disable(:free_user_cap)
       2. Feature.enable(:free_user_cap_new_namespaces)
       3. Gitlab::CurrentSettings.update(dashboard_limit_new_namespace_creation_enforcement_date: g.created_at - 1.day)
    Screenshot

    

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