[Roots] Move my-items to separate bundle

My Items root is now opt-in, and does not need to be enabled for all
deployments.  My Items is enabled by default in the development edition.

https://github.com/nasa/openmct/issues/1251

src/defaultRegistry.js

@@ -71,6 +71,7 @@ define([
     '../platform/features/conductor-v2/utcTimeSystem/bundle',
     '../platform/features/imagery/bundle',
     '../platform/features/layout/bundle',
+    '../platform/features/my-items/bundle',
     '../platform/features/pages/bundle',
     '../platform/features/plot/bundle',
     '../platform/features/static-markup/bundle',