I initially wanted to do the refactoring in a separate merge request, but since my merge request yesterday broke the tests, I decided to add the implementation into this commit as well.
-- v5: kernelbase: Recursively obtain the Wow6432Node parent. kernelbase: Add support for shared registry keys. kernelbase: Call create_key() from create_subkey(). kernelbase: Factor creating a subkey out of create_key(). kernelbase: Don't open Wow6432nodes from create_key().