kernel/thread: Include thread-related enums within the kernel namespace

Previously, these were sitting outside of the Kernel namespace, which
doesn't really make sense, given they're related to the Thread class
which is within the Kernel namespace.

src/core/hle/service/service.cpp

@@ -198,11 +198,12 @@ void ServiceFrameworkBase::HandleSyncRequest(SharedPtr<ServerSession> server_ses
     handler_invoker(this, info->handler_callback, context);
 
     auto thread = Kernel::GetCurrentThread();
-    ASSERT(thread->status == ThreadStatus::Running || thread->status == ThreadStatus::WaitHleEvent);
+    ASSERT(thread->status == Kernel::ThreadStatus::Running ||
+           thread->status == Kernel::ThreadStatus::WaitHleEvent);
     // Only write the response immediately if the thread is still running. If the HLE handler put
     // the thread to sleep then the writing of the command buffer will be deferred to the wakeup
     // callback.
-    if (thread->status == ThreadStatus::Running) {
+    if (thread->status == Kernel::ThreadStatus::Running) {
         context.WriteToOutgoingCommandBuffer(cmd_buf, *Kernel::g_current_process,
                                              Kernel::g_handle_table);
     }