Add EmptyState component to new Vue To-Do app

What does this MR do and why?

This MR is about the new, unreleased Vue implementation of the To-do feature (dashboard/todos/vue). Closes #483059 (closed)

It renders an EmptyState component when there are no todos to show, the same way to old Haml implementation does:

• when the user never ever had a todo, we show the same Haml page. (no change)
• when the user has no pending todos, we show an empty state where the title is random from a pool of possible titles (now same as in Haml)
• when the user has no pending todos found while a filter is active, we show a different message (but same as Haml does)

MR acceptance checklist

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Screenshots or screen recordings

No pending todos

Before	After

No filtered todos

Before	After

How to set up and validate locally

• Enable the todos_vue_application feature flag.
• Go to http://gdk.test:3000/dashboard/todos/vue (Note the /vue at the end of the URL)
• Check with 0 pending todos
• Check with 0 filtered todos
• Compare to the old implementation (/dashboard/todos)