Fix EZP-21438: Improve permission handling to use view_embed

### Description ###

Currently, load methods in contentService check for valid content/read access.
However, it is possibly that users (only) have the `view_embed` permission.

This allows for content to be rendered, from twig, using the embed viewType, if the user has view_embed permissions:
```
{{ render( controller( "ez_content:viewContent", {"contentId": 123, "viewType": "embed"} ) ) }}
```

### Tests ###
Manual testing