Fix EZP-23594: It's not possible to use custom controllers for embed (inline) views

JIRA issue: https://jira.ez.no/browse/EZP-23594

`EmbedToHtml5` `XmlText` converter directly uses the view manager to render content, while it should use subrequests to render content.

Since subrequest is not used, `ViewControllerListener` never gets triggered, which in turn means that custom controller cannot be used.

This pull requests replaces view manager with Symfony fragment handler to call the subrequest on `ez_content:viewContent` or `ez_content:viewLocation`.