Consolidate and merge functionality of the RichTextModel and ChildFacetUuidsModel

The refactoring and solution of CMS7-1610 for the ChildFacetUuidsModel introduced a second HtmlCleaner instance and processing of html fields besides the (optional) processing by the HtmlCleanerPlugin.
This is not a desirable situation as CMS7-8616 already showed:

• html parsing and rewriting is now done twice
• the ChildFacetUuidsModel uses a none configurable (hard-coded) HtmlCleaner, which may not by aligned with the HtmlCleanerPlugin

After thorough discussion the following solution has been decided to resolve this:

• use a single HtmlCleaner instance, as configured through the HtmlCleanerPlugin repository configuration
• this requires that the HtmlCleanerPlugin service always is used: if for a field the htmlcleaner.id is configured empty (null), then use and fallback to the 'default' org.hippoecm.frontend.plugins.richtext.IHtmlCleanerService
  but (then) with whitelisting filtering disabled
• the HtmlCleanerService will also get a new optional configuration property to enable/disable whitelisting explicitely (default true) which is useful and needed to support two or more HtmlCleanerService instances
• the RichTextModel will be refactored to get a ChildFacetUuidsModel optionally injected (instead of being wrapped by one)
• the RichTextModel will get an instantiated HtmlCleaner from the HtmlCleanerPlugin and create a TagNode from the html text with it
• this html TagNode then will first be passed into the ChildFacetUuidsModel (not used for the CKEditorPropertyPlugin) instead of the html text, which can modify it as needed
• thereafter the html TagNode will be passed into the HtmlCleanerPlugin to do (optional) whitelist filtering and the final serializing to a html string value