Kernel+Userland: Add ioctl to set process ownership of DisplayConnector

Now that the infrastructure of the Graphics subsystem is quite stable,
it is time to try to fix a long-standing problem, which is the lack of
locking on display connector devices. Reading and writing from multiple
processes to a framebuffer controlled by the display connector is not a
huge problem - it could be solved with POSIX locking.

The real problem is some program that will try to do ioctl operations on
a display connector without the WindowServer being aware of that which
can lead to very bad situations, for example - assuming a framebuffer is
encoded at a known resolution and certain display timings, but another
process changed the ModeSetting of the display connector, leading to
inconsistency on the properties of the current ModeSetting.

To solve this, there's a new "master" ioctl to take "ownership" and
another one to release that ownership of a display connector device. To
ensure we will not hold a Process object forever just because it has an
ownership over a display connector, we hold it with a weak reference,
and if the process is gone, someone else can take an ownership.

Kernel/API/Graphics.h

@@ -50,6 +50,16 @@ ALWAYS_INLINE int graphics_connector_get_head_edid(int fd, GraphicsHeadEDID* inf
     return 0;
 }
 
+ALWAYS_INLINE int graphics_connector_set_responsible(int fd)
+{
+    return ioctl(fd, GRAPHICS_IOCTL_SET_RESPONSIBLE, nullptr);
+}
+
+ALWAYS_INLINE int graphics_connector_unset_responsible(int fd)
+{
+    return ioctl(fd, GRAPHICS_IOCTL_UNSET_RESPONSIBLE, nullptr);
+}
+
 ALWAYS_INLINE int fb_get_head_vertical_offset_buffer(int fd, GraphicsHeadVerticalOffset* vertical_offset)
 {
     return ioctl(fd, GRAPHICS_IOCTL_GET_HEAD_VERTICAL_OFFSET_BUFFER, vertical_offset);