Use route provider, not statically generated YAML routes, for content entities

[Crell]

And probably for config entities, too. 😄

We're trying to actively discourage manually created routes for entities. Instead, the generated annotation should reference the default route provider. It will then generate appropriate routes on the fly based on the links array on the entity.

[bojanz]

Where are you seeing static routes? Both content and config entities use the DefaultHtmlRouteProvider.

[bojanz]

Related: #2022 (since it will remove the custom add-form implementation)

[Crell]

Hm, perhaps I have an old copy of console installed? I generated a content entity, and ended up with several new routes defined. (I've since deleted them as this entity doesn't even have a UI.)

[hjuarez20]

See #1849, we will change the way how we render the routes