`bevy_ui_widgets` needs some dependencies (#24472)

It panicked if you started the app with DefaultPlugins, because some
resources were missing.

# Objective

Fix panic when starting the app with `bevy_ui_widgets` or
`bevy_feathers` but no `ui` feature.

Fixes #24369

## Solution

Add the needed features as feature dependencies.

The alternative would be to make `bevy_ui_widgets` work without them,
and that could be considered.
One could replace the `Res<...>` with `If<...>` for example. Downside:
silently missing capabilities.

## Testing

I compiled and ran the example from the issue.