Updated management API endpoint and model for data type references to align with that used for documents, media etc. (#18905)

* Updated management API endpoint and model for data type references to align with that used for documents, media etc.

* Refactoring.

* Update src/Umbraco.Core/Constants-ReferenceTypes.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Fixed typos.

* Added id to tracked reference content type response.

* Updated OpenApi.json.

* Added missing updates.

* Renamed model and constants from code review feedback.

* Fix typo

* Fix multiple enumeration

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: mole <nikolajlauridsen@protonmail.ch>

tests/Umbraco.Tests.Common/Builders/MediaTypeBuilder.cs

@@ -139,6 +139,7 @@ public class MediaTypeBuilder
         var mediaType = builder
             .WithAlias(alias)
             .WithName(name)
+            .WithIcon("icon-picture")
             .WithParentContentType(parent)
             .AddPropertyGroup()
             .WithAlias(propertyGroupAlias)