Remove RTE embedded image handling + clean up file upload configuration (#16025)

src/Umbraco.Core/PropertyEditors/FileUploadConfiguration.cs

@@ -3,8 +3,8 @@ namespace Umbraco.Cms.Core.PropertyEditors;
 /// <summary>
 ///     Represents the configuration for the file upload address value editor.
 /// </summary>
-public class FileUploadConfiguration : IFileExtensionsConfig
+public class FileUploadConfiguration
 {
     [ConfigurationField("fileExtensions")]
-    public List<FileExtensionConfigItem> FileExtensions { get; set; } = new();
+    public IEnumerable<string> FileExtensions { get; set; } = Enumerable.Empty<string>();
 }

src/Umbraco.Core/PropertyEditors/IFileExtensionConfig.cs

@@ -1,9 +0,0 @@
-namespace Umbraco.Cms.Core.PropertyEditors;
-
-/// <summary>
-///     Marker interface for any editor configuration that supports defining file extensions
-/// </summary>
-public interface IFileExtensionsConfig
-{
-    List<FileExtensionConfigItem> FileExtensions { get; set; }
-}