batches: admin batch spec executions list view
Created by: courier-new
Closes #23032 (closed) (and maybe EM1.3???).
Adds a basic admin list view of the most recently executed batch specs, only visible when the feature flag is turned on. See storybook story. From the list view you can get back to any individual execution that happened.
This is mostly just a tool for us for debugging but also provides insights and UI for what information we care to surface about historical execution runs, which we can likely reuse for other list views in the future.