[PATCH 0/4] MR943: uiautomationcore: Add more nested node features. (v2)

[Connor McAdams (＠cmcadams)]

Changes since last MR:
- Store list entry inside of `struct uia_node` instead of doing linear search for removal.
- Replace `WARN` with `ERR` if provider thread shuts down with nodes still in the provider thread list.
- Use `wine/rbtree.h` for looking up HUIANODEs by runtime ID.
- Get rid of `struct uia_node *container_node` inside of `struct uia_provider`.