AK: Rename the common integer typedefs to make it obvious what they are.

These types can be picked up by including <AK/Types.h>:

* u8, u16, u32, u64 (unsigned)
* i8, i16, i32, i64 (signed)

Kernel/init.cpp

@@ -50,7 +50,7 @@ VFS* vfs;
 #ifdef STRESS_TEST_SPAWNING
 [[noreturn]] static void spawn_stress()
 {
-    dword last_sum_alloc = sum_alloc;
+    u32 last_sum_alloc = sum_alloc;
 
     for (unsigned i = 0; i < 10000; ++i) {
         int error;