Fix splash screen upside down on Android

Fixes an issue introduced in #96439 (see
https://github.com/godotengine/godot/pull/96439#issuecomment-2447288702)

Godot was relying on Java's
activity.getWindowManager().getDefaultDisplay().getRotation(); to apply
pre-rotation but this is wrong.

First, getRotation() may temporarily return a different value from the
correct one; which is what was causing the splash screen to be upside
down. It would return -90 instead of 90 for the first rendered frame.

But unfortunately, the splash screen is just one frame rendered for a
very long time, so the error lingered for a long time for everyone to
see.

Second, to determine what rotation to use, we should be looking at what
Vulkan told us, which is the value we pass to
VkSurfaceTransformFlagBitsKHR::preTransform.

This commit removes the now-unnecessary
screen_get_internal_current_rotation() function (which was introduced by
#96439) and now saves the preTransform value in the swapchain.

platform/android/java/lib/src/org/godotengine/godot/GodotIO.java

@@ -296,28 +296,6 @@ public class GodotIO {
 		}
 	}
 
-	/**
-	 This function is used by DisplayServer::screen_get_internal_current_rotation (C++)
-		and is used to implement a performance optimization in devices that do not offer
-		a HW rotator.
-	 @return
-		Rotation in degrees, in multiples of 90°
-	*/
-	public int getInternalCurrentScreenRotation() {
-		int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
-
-		switch (rotation) {
-			case Surface.ROTATION_90:
-				return 90;
-			case Surface.ROTATION_180:
-				return 180;
-			case Surface.ROTATION_270:
-				return 270;
-			default:
-				return 0;
-		}
-	}
-
 	public void setEdit(GodotEditText _edit) {
 		edit = _edit;
 	}