Add Transfer Tab to conditionally render in CE

What does this MR do and why?

This implements Add Transfer tab/app to conditionally render in CE (#393443 - closed)

• This piece is under usage_quotas_for_all_editions Feature Flag.
• The Transfer Tab is under data_transfer_monitoring Feature Flag.

Now that we finished with #440195 (closed), i.e. after we merge !143633 (merged) and !143637 (merged), we're now able to migrate other tabs. The migration here is simpler because we just need to conditionally render this tab.

In other words: This tab will be hooked to an App that is in CE but will only render in EE.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

usage_quotas_for_all_editions off	usage_quotas_for_all_editions on

How to set up and validate locally

Enable Transfer Tab

1. Enable the data_transfer_monitoring feature flag
   • bin/rails console
   • Feature.enable(:data_transfer_monitoring)
2. Seed the data
   • Open the console bin/rails console
   • Go to https://gitlab.com/-/snippets/2522604
   • Copy the class code and paste it in the console
   • Find a group with some projects in it and make note of the group id (displayed on the overview page)
   • Run PopulateDataTransfer.run(<group_id>) in the console; e.g. PopulateDataTransfer.run(89)
   • Press q then type exit to get back to the normal command prompt
3. Navigate to your group -> Settings -> Usage quotas
4. Click on the Transfer tab

The expected behavior

We need to validate this in 4 scenarios:

1. GitLab EE Unlicensed: this is probably how your GDK is right now. If you have a license in your GDK, remove it in https://gdk.test:3443/admin/subscription
2. GitLab EE: by having a test license in your GDK.
3. GitLab SaaS: setup a license like the above and simulate SaaS
4. GitLab CE: by executing
   1. export FOSS_ONLY=1
   2. gdk restart
   3. Tanuki gdk website icon (the one in the browser tab) should be blue, then you're in CE

Now go to your Group Usage Quotas: https://gdk.test:3443/groups/<your-group-here>/-/usage_quotas and check if your local setup matches the expected behavior.

• To enable the FF: Feature.enable(:usage_quotas_for_all_editions)
• To disable the FF: Feature.disable(:usage_quotas_for_all_editions)

Expected behavior: