Create reusable upload dropzone field for integrations

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As discussed in !111621 (comment 1291282054), I'm creating this issue to track the work to convert the upload dropzone components created for the Apple App Store and Google Play integrations into a reusable field that can be configured from the Integrations DSL.

The existing Apple App Store component can be referenced here: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/integrations/edit/components/sections/apple_app_store.vue