Outputs: Defensive checks, and don't wait for a Metal drawable twice in a frame

- Metal: when a layer has no drawable to give (it can take a second to
  say so), don't ask again in the same frame for every pass to it.
- Swapchains other than the primary are created, resized and destroyed
  between frames (Metal asserts it), and destroyed with the last
  reference to them (ReleaseAssertLast, Metal and Vulkan).
- BindFramebufferSamplesAsTexture asserts it isn't given a swapchain,
  like BindFramebufferAsTexture.
- An offscreen Metal swapchain can't be resized, asserted.
- VulkanRenderManager asserts that no additional swapchain outlives it.
- Native_RemoveOutputAndWait asserts it isn't called on the thread that
  handles the requests, where it would always time out.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Common/GPU/Vulkan/VulkanRenderManager.cpp

@@ -759,6 +759,8 @@ void VulkanRenderManager::CheckNothingPending() {
 
 VulkanRenderManager::~VulkanRenderManager() {
 	INFO_LOG(Log::G3D, "VulkanRenderManager destructor");
+	// Their owners (the outputs) destroy them first, on device loss. Left over, they'd outlive the device.
+	_dbg_assert_(extraSwapchains_.empty());
 
 	{
 		std::unique_lock<std::mutex> lock(compileQueueMutex_);