Fix/471 extension service providers (#472)

* Recursively look for generic type arguments on a profile to filter for ServiceConstraint

* Fix BaseExtensionService profile type expected in constructor

* Update XRTK-Core/Packages/com.xrtk.core/Inspectors/Profiles/MixedRealityServiceProviderProfileInspector.cs

Co-Authored-By: Stephen Hodgson <StephenHodgson@users.noreply.github.com>

* Update XRTK-Core/Packages/com.xrtk.core/Extensions/TypeExtensions.cs

Co-Authored-By: Stephen Hodgson <StephenHodgson@users.noreply.github.com>

* Update XRTK-Core/Packages/com.xrtk.core/Definitions/BaseMixedRealityExtensionServiceProfile.cs

Co-Authored-By: Stephen Hodgson <StephenHodgson@users.noreply.github.com>

* Fix class doc

* Fix missing using

* Fix base extension service profile generic type

* Make ServiceConstraint protected to allow for custom override

* Update Tests

* Fix interface base type

* Fix extension service configurations registration

Co-authored-by: Stephen Hodgson <StephenHodgson@users.noreply.github.com>

Services/MixedRealityToolkit.cs

@@ -479,7 +479,7 @@ private void InitializeServiceLocator()
                 {
                     if (CreateAndRegisterService(configuration))
                     {
-                        if (configuration.ConfigurationProfile is BaseMixedRealityExtensionDataProviderProfile extensionServiceProfile)
+                        if (configuration.ConfigurationProfile is BaseMixedRealityExtensionServiceProfile extensionServiceProfile)
                         {
                             RegisterServices(extensionServiceProfile.RegisteredServiceConfigurations);
                         }