Add Swappy & Pre-Transformed Swapchain

- Adds Swappy for Android for stable frame pacing
- Implements pre-transformed Swapchain so that Godot's compositor is in
charge of rotating the screen instead of Android's compositor
(performance optimization for phones that don't have HW rotator)

============================

The work was performed by collaboration of TheForge and Google. I am
merely splitting it up into smaller PRs and cleaning it up.

Changes from original PR:

- Removed "display/window/frame_pacing/android/target_frame_rate" option
to use Engine::get_max_fps instead.
- Target framerate can be changed at runtime using Engine::set_max_fps.
- Swappy is enabled by default.
- Added documentation.
- enable_auto_swap setting is replaced with swappy_mode.

drivers/vulkan/rendering_device_driver_vulkan.h

@@ -142,6 +142,11 @@ class RenderingDeviceDriverVulkan : public RenderingDeviceDriver {
 	bool device_fault_support = false;
 #if defined(VK_TRACK_DEVICE_MEMORY)
 	bool device_memory_report_support = false;
+#endif
+#if defined(SWAPPY_FRAME_PACING_ENABLED)
+	// Swappy frame pacer for Android.
+	bool swappy_frame_pacer_enable = false;
+	uint8_t swappy_mode = 2; // See default value for display/window/frame_pacing/android/swappy_mode.
 #endif
 	DeviceFunctions device_functions;
 
@@ -350,9 +355,13 @@ private:
 		LocalVector<uint32_t> command_queues_acquired_semaphores;
 		RenderPassID render_pass;
 		uint32_t image_index = 0;
+#ifdef ANDROID_ENABLED
+		uint64_t refresh_duration = 0;
+#endif
 	};
 
 	void _swap_chain_release(SwapChain *p_swap_chain);
+	VkExtent2D native_display_size;
 
 public:
 	virtual SwapChainID swap_chain_create(RenderingContextDriver::SurfaceID p_surface) override final;
@@ -360,6 +369,7 @@ public:
 	virtual FramebufferID swap_chain_acquire_framebuffer(CommandQueueID p_cmd_queue, SwapChainID p_swap_chain, bool &r_resize_required) override final;
 	virtual RenderPassID swap_chain_get_render_pass(SwapChainID p_swap_chain) override final;
 	virtual DataFormat swap_chain_get_format(SwapChainID p_swap_chain) override final;
+	virtual void swap_chain_set_max_fps(SwapChainID p_swap_chain, int p_max_fps) override final;
 	virtual void swap_chain_free(SwapChainID p_swap_chain) override final;
 
 	/*********************/