Integrate Announcements into Navigation's drawer/submenu

Not sure if the component needs to be Navigation or Announcements, so leaving into Navigation for now because we need to provide the designs and styles at least.

In progress

Here is very raw implementation https://git.drupalcode.org/project/drupal/-/merge_requests/9069

I'm fetching the list of announcements and simulating from them the child menu for parent `Announcements` link. For now visually it is looking similar now as other dropmenus.

I prepared this MR mostly to give front devs to do their job separately. Now we have the full data available in twig and we can build UI fully matchined desired design, while backenders can work on the implementation.

Here are few thouhgs:
1. For the old `toolbar` module `announcements_feed` module is injecting the whole structure from inside, instead of `toolbar` module is relying on `announcements_feed`. Should we have the same logic? Like to put child menu into our navigation sidebar from using code written in `announcements_feed` module ?
2. In the old `toolbar` module `Annoucements` link doesn't have child menu by default. Instead it's a link to another page '/admin/announcements_feed' and in the same time it's an ajax link which is getting on response dialog with child menu links. Should we have ajax here aswell? For now there is no ajax in my MR.
3. Specific design for child menu of `Annoucements` will require probably new unique `theme hook` <- so potentlially it will not be a part of `navigation-menu.html.twig` component.

Keeping ticket on `Active` status since it requires discussions / Design.

Added designs to the issue summary. This is ready to be worked on.

I think this issue should be moved into the Announcements issue queue, no?