vulkan: rework {Create,Destroy}Device_Bottom

The reworked driver::CreateDevice will

 - use the providied pAllocator,
 - call HAL's EnumerateDeviceExtensionProperties and filter out extensions
   unknown to HAL, if there is any extension enabled.

We do not expect or enumerate any HAL layer yet as that requires some
works to layers_extensions.cpp.

Change-Id: I3ba4019d18dfed994d7037d95825bf54096f2a5d