Merge changes I97efd6c9,I6460f8f0,Ic67e4290,I16214514,Ieaa4e463, ... into nyc-dev

Merge changes I97efd6c9,I6460f8f0,Ic67e4290,I16214514,Ieaa4e463, ... into nyc-dev

* changes:
  vulkan: remove g_device_layers
  vulkan: ignore device-only layers
  vulkan: ignore layer libraries without instance layers
  vulkan: add FindLayer helper
  vulkan: constify LayerRef members
  vulkan: make g_library_mutex per-LayerLibrary
  vulkan: make LayerLibrary a class
  vulkan: refactor GetLayerGetProcAddr
  vulkan: refactor AddLayerLibrary
  vulkan: refactor LayerRef::~LayerRef
  vulkan: refactor GetLayerRef
  vulkan: add a constructor for LayerLibrary