[vulkan] Only retrieve host physical devices once

bug: 111137294

The handles need to stay the same between invocations.

This CL takes the codegen that makes vkEnumeratePhysicalDevices
a custom implementation, and only asks the host once
for the physical device handles.

Test: Unit test
Change-Id: Ib07f1f14c41e973fee284a48275d1625941007b9