Kernel: Implement supplementary groups

This code has very ugly file parsing code. I have to create API
for reading files line by line in kernel space...

This allows users to open framebuffer/input files without root.

Mounting has to be moved to userspace soon. It makes no sense to
hard code permissions for every (device) file.

kernel/kernel/Input/PS2Controller.cpp

@@ -69,7 +69,7 @@ namespace Kernel::Input
 	static PS2Controller* s_instance = nullptr;
 
 	PS2Device::PS2Device()
-		: CharacterDevice(0440, 0, 0)
+		: CharacterDevice(0440, 0, 901)
 		, m_name(BAN::String::formatted("input{}", DevFileSystem::get().get_next_input_device()))
 	{ }