This begins paving the way for removal of user access to kernel
address space.
After the previous commits, BDirectWindow and BWindowScreen
still function properly.
Part of #19990.
Change-Id: I8477e43cd517ba67383755a4cb60b00bc117f5d7
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10559
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>