Change Admin controller CloudLicenses to Subscriptions

What does this MR do?

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/332838

The Admin::CloudLicensesController is renamed to Admin::SubscriptionsController to make its naming for neutral for the two use cases of licenses.

This also required to change the folder structure for the frontend files which were under ee/app/assets/javascripts/pages/admin/cloud_licenses/. After looking into a frontend issue with @mlunoe, he noticed that the files are in the wrong place and not like the other existing file structures. Therefore everything was moved from ee/app/assets/javascripts/pages/admin/cloud_licenses/ to ee/app/assets/javascripts/admin/subscriptions/show/.

While already at it, we also moved the qrtly_reconciliation_alert frontend files from ee/app/assets/javascripts/admin/ to ee/app/assets/javascripts/admin/qrtly_reconciliation_alert/.

No changelog required as the functionality is behind an application setting that hasn't been enabled yet and other changes are developer facing.

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