[K/N][Runtime] Separate thread registering and making it 'Runnable'

The new GC will require threads to suspend right after registering
if Stop-The-World is requested. This patch changes the initial
thread state to kNative and adds a separate state switch right
after thread registering. This switch suspends if it is necessary.

kotlin-native/runtime/src/mm/cpp/Memory.cpp

@@ -95,8 +95,13 @@ extern "C" MemoryState* InitMemory(bool firstRuntime) {
 }
 
 extern "C" void DeinitMemory(MemoryState* state, bool destroyRuntime) {
+    // We need the native state to avoid a deadlock on unregistering the thread.
+    // The deadlock is possible if we are in the runnable state and the GC already locked
+    // the thread registery and waits for threads to suspend or go to the native state.
+    AssertThreadState(state, ThreadState::kNative);
     auto* node = mm::FromMemoryState(state);
     if (destroyRuntime) {
+        ThreadStateGuard guard(state, ThreadState::kRunnable);
         node->Get()->gc().PerformFullGC();
         // TODO: Also make sure that finalizers are run.
     }