Deprecate old SharePoint

This PR deprecates the `mssp` and `od4b` backends as they stopped working when the APIs were turned off.

The upgrade path is to use `sharepoint` instead (which used to be named "SharePoint v2").

This PR also adds a small amount of metadata to modules so they can be marked as "untested" or "deprecated", and the configuration for marking modules has been set up in `BackendModules.cs`.

The backends that we currently cannot test (usualy due to not having public signups) are now marked as untested.

Duplicati/Server/Duplicati.Server.Serialization/Interface/IDynamicModule.cs

@@ -49,6 +49,14 @@ namespace Duplicati.Server.Serialization.Interface
         /// The lookups supported by the module
         /// </summary>
         IDictionary<string, IDictionary<string, string>> Lookups { get; }
+        /// <summary>
+        /// Indicated the module is deprecated
+        /// </summary>
+        bool IsDeprecated { get; }
+        /// <summary>
+        /// Indicated the module is untested
+        /// </summary>
+        bool IsUntested { get; }
     }
 }