Fix EZP-23513: embed rendering (RichText)

This PR resolves https://jira.ez.no/browse/EZP-23513

Part 2 of 2, handling RichText field type.
Part 1 of 2 for XmlText can be found here: https://github.com/ezsystems/ezpublish-kernel/pull/1087

Continuing on #1087, this adds embed linking capabilities to native RichText format. Link is added as separate child element, like:

```xml
<ezembed xlink:href="ezcontent://106" view="embed" xml:id="embed-id-1" ezxhtml:class="embed-class" ezxhtml:align="left">
  <ezlink xlink:href="ezurl://95#fragment1" xlink:show="new" xml:id="link-id-1" xlink:title="Link title" ezxhtml:class="link-class"/>
  <ezconfig>
    <ezvalue key="size">medium</ezvalue>
    <ezvalue key="offset">10</ezvalue>
    <ezvalue key="limit">5</ezvalue>
  </ezconfig>
</ezembed>
```

For Docbook and XHTML5 edit formats, a Schematron rule is added, preventing `ezlink` element from appearing in `link` or `a` elements. This would be possible to achive in RELAX NG and XSD, but it would be very awkward, so I went with this solution as we already support Schematron validation.

Embed parameters passed to the rendering process are here changed, example:

```php
"embedParams" => array(
    "id" => "601",
    "viewType" => "embed-inline",
    "config" => array(
        "size" => "medium",
        "offset" => 10,
        "limit" => 5,
    ),
    "link" => array(
        "href" => "http://www.example.com",
        "resourceType" => "CONTENT",
        "resourceId" => "95",
        "resourceFragmentIdentifier" => "fragment1",
        "wrapped" => false,
        "title" => "Link title",
        "target" => "_self",
    ),
),
```

With this, properties will not be available if empty, e.g. if title is not defined on a link it will not be present, or if embed is not linked `link` will not be present among the `embedParams` in the template.
XmlText implementation is here changed to the same style. It is also updated with new `resourceFragmentIdentifier` parameter.

RichText's default embed templates are updated for this, however care is taken to pass the parameters to the sub-request in the form we currently support, so there is no BC break. If a user wants to have full new `embedParams` in the end template, only default template change is needed.
#### Followups:
* [EZP-23646](https://jira.ez.no/browse/EZP-23646): Docbook->EZXML conversion tmp paragraphs (PR: https://github.com/ezsystems/ezpublish-kernel/pull/1092)
* [EZP-23647](https://jira.ez.no/browse/EZP-23647): Link parameters for externally linked embeds
* [EZP-23648](https://jira.ez.no/browse/EZP-23648): Implement UrlService
* [EZP-23650](https://jira.ez.no/browse/EZP-23650): Clean up URL resolving in XmlText and RichText external storages