Netcore: Turn container validation back on (#9401)

* Remove RuntimeLevelAttribute & disable filtering

* Remove RuntimeLevelAttribute usage on Composers

* Fix broken tests

* Resolve UserManager registration issues.

* Turn container validation back on.

* Resolve lifetime issue post install backoffice.

* Remove final TODO: MSDI

src/Umbraco.Tests.Integration/Testing/IntegrationTestComposer.cs

@@ -35,7 +35,6 @@ namespace Umbraco.Tests.Integration.Testing
     /// <remarks>
     /// This is a IUserComposer so that it runs after all core composers
     /// </remarks>
-    [RuntimeLevel(MinLevel = RuntimeLevel.Boot)]
     public class IntegrationTestComposer : ComponentComposer<IntegrationTestComponent>
     {
         public override void Compose(Composition composition)