Build pipeline subscriptions table

What does this MR do and why?

Part two: Refactoring pipeline subscriptions feature to Vue/Graphql

Goal of this MR

1. Build reusable table component for upstream/downstream subscriptions
2. Lay ground work for add new button and delete subscriptions (hooking up in future MRs)
3. Add test coverage

You can view rough outline of the following steps during this refactor here &11446

Part one: !139405 (merged)

Part two: This MR is part two

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

Before	After

How to set up and validate locally

1. Enable feature flag in rails console pipeline_subscriptions_vue
2. Visit Project > Settings > CI/CD > Expand pipeline subscriptions
3. Verify everything is working as expected

Related to #425292 (closed)