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.

platform/android/java_godot_io_wrapper.h

@@ -61,6 +61,7 @@ private:
 	jmethodID _has_hardware_keyboard = 0;
 	jmethodID _set_screen_orientation = 0;
 	jmethodID _get_screen_orientation = 0;
+	jmethodID _get_internal_current_screen_rotation = 0;
 	jmethodID _get_system_dir = 0;
 
 public:
@@ -88,6 +89,7 @@ public:
 	void set_vk_height(int p_height);
 	void set_screen_orientation(int p_orient);
 	int get_screen_orientation();
+	int get_internal_current_screen_rotation();
 	String get_system_dir(int p_dir, bool p_shared_storage);
 };