Add "GetAll" method to ISettingDefinitionContext

Its implementation class already has the implementation method for "GetAll"

framework/src/Volo.Abp.Settings/Volo/Abp/Settings/ISettingDefinitionContext.cs

@@ -3,7 +3,9 @@
     public interface ISettingDefinitionContext
     {
         SettingDefinition GetOrNull(string name);
+        
+        IReadOnlyList<SettingDefinition> GetAll();
 
         void Add(params SettingDefinition[] definitions);
     }
-}
+}