Revert "[Core] Get rid of some of our asynchronous initialisation when running mdtool"

This reverts commit 6ac5b1c5e34c7a9346c120969ca846d949bfab3b.

It slows down all mdtool invocations by several seconds to work
around issues in the setup tool.
[Core] Add method for getting addin registry location
[mdtool] When running setup tool, only initialize addin registry