Kernel/Graphics: Introduce a new mechanism to initialize a PCI device

Instead of using a clunky switch-case paradigm, we now have all drivers
being declaring two methods for their adapter class - create and probe.
These methods are linked in each PCIGraphicsDriverInitializer structure,
in a new s_initializers static list of them.
Then, when we probe for a PCI device, we use each probe method and if
there's a match, then the corresponding create method is called.

As a result of this change, it's much more easy to add more drivers and
the initialization code is more readable.

Kernel/Graphics/GraphicsManagement.h

@@ -50,7 +50,7 @@ public:
 private:
     void enable_vga_text_mode_console_cursor();
 
-    bool determine_and_initialize_graphics_device(PCI::DeviceIdentifier const&);
+    ErrorOr<void> determine_and_initialize_graphics_device(PCI::DeviceIdentifier const&);
 
     void initialize_preset_resolution_generic_display_connector();