Add a script service to execute rendering transformations

We already have a script service to parse and render the content. We're missing a script service to execute the rendering transformations. I would like to be able to do something like this:

#set ($targetSyntax = 'uniast/1.0')
#set ($xdom = $services.rendering.parse($tdoc.content, $tdoc.syntax))
#set ($discard = $services.rendering.transform($xdom
  ).withSyntax($tdoc.syntax
  ).withTargetSyntax($targetSyntax
  ).withRestricted(true
  ).withTransformations(['macro']
  ).withContentDocument($tdoc.documentReference
  ).execute())
#set ($renderedContent = $services.rendering.render($xdom, $targetSyntax))

See https://forum.xwiki.org/t/new-services-rendering-transform-api/18175 .

Note that this is needed for BlockNote integration, which uses the Edit Module, which allows having a template as the entry point for loading the editor. When loading the editor we need to "convert" the content of the edited document from the source syntax to the syntax supported by BlockNote (UniAst). We need to execute the rendering transformations when performing this conversion.