vulkan/overlay: deal with unknown pNext structures

To implement some of the features of the layer, we need to enable some of the feature bits at device/command_buffer creation. To do so, we need to edit some of the structures coming from the application. Most of those are const so we need to clone them before edition.

This change disables some of the layer features if we run into a situation where one of the structure we need to clone is unknown such that we can't make a copy of it (since we don't know its size).

Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Closes: #7677 (closed)