Implement container virtual registries list UI

Context

GraphQL API to query container virtual registries was added in Get a list of the container virtual registries ... (#579595 - closed)

Proposal

Implement the page similar to https://gitlab.com/gitlab-org/gitlab/-/work_items/493842/designs/Virtual-registries-list-by-type.png

But the final state should look like screenshots in Add table headers for maven virtual registries ... (!209081 - merged)

• Add registries_and_upstreams controller and route on the backend
• Use new feature flag to control the frontend
• No need of adding tabs yet.
• Show registries in a table format.