kern: fully implement slabheap init

libraries/libmesosphere/include/mesosphere/board/nintendo/switch/kern_k_system_control.hpp

@@ -36,6 +36,10 @@ namespace ams::kern {
                     static u64  GenerateRandomRange(u64 min, u64 max);
             };
         public:
+            /* Randomness. */
+            static void GenerateRandomBytes(void *dst, size_t size);
+            static u64  GenerateRandomRange(u64 min, u64 max);
+
             /* Panic. */
             static NORETURN void StopSystem();
     };