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.