vulkan/ios: remove uiview retrieval race

commit 0c5390ba

applemedia/videocache: remove unimplemented/used upload function

commit dc1f934b

vulkan/window/ios: fix race on window startup

1. The iOS create_surface implementation needs to call out to the main
thread to create the window (UIKit requirement)
2. get_surface() can be called and will attempt to create the VkSurface
from an invalid view/layer.

Also pass the layer for MoltenVK so we don't get pesky 'UIView function
not called on main thread' warnings.

commit 56d2a09f

vulkan: create the macos/ios-specific displays

commit f24512be

vulkan: install public gstvkdebug.h header