Revert "build: Restore default symbol visibility to layers/tests"
Revert "build: Restore default symbol visibility to layers/tests"

This reverts commit dd96dd21b438d48aa78e9de60ad0c550c856cf29.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools