libvulkan: make vkEnumerateInstanceVersion trigger driver loading

This is a globally dispatched api, and it's the best option to preload
the driver in Zygote with minimum overhead.

This change also updates some return codes according to the spec.

Bug: 135536511
Test: take a trace and verify driver is loaded
Change-Id: I6fe425ec568b13577d3d9471aa5f181cff44c61c