When updating the foreground window, even if both the old and new active
window belong to the same non-current thread, the win32u code currently
explicitly deactivates the old window. This will cause the transient
deactivation of the foreground thread which can lead to undesirable
side-effects (e.g., some apps may minimize when they become inactive).

Until this is fixed in Wine core, use an internal driver message to
ensure that we call NtUserSetForegroundWindow from the context of
the new foreground window thread, to avoid the problematic behavior.