Mark some methods of Kernel noexcept because control flow is odd.

Some methods of Kernel, such as vanish(), have odd control flow. Let's
mark these methods "noexcept" to prevent exceptions from being thrown
across these bounaries.

Kernel/include/kernel.hpp

@@ -27,19 +27,19 @@ class Kernel : private KernelPolicy {
     void run();
 
     // Redirect the interrupt to the appropriate handler.
-    void dispatch_interrupt(void* params)
+    void dispatch_interrupt(void* params) noexcept
     {
         interrupt_controller_.dispatch(params);
     }
 
     // The current thread yields to the next runnable thread.
-    void yield()
+    void yield() noexcept
     {
         scheduler_.yield();
     }
 
     // The current thread exits.
-    __attribute__((noreturn)) void vanish()
+    __attribute__((noreturn)) void vanish() noexcept
     {
         scheduler_.vanish();
     }