vulkan: Add inital vram-report-limit layer

This Vulkan layer allows reporting a limited VRAM size to the application. This layer can be useful for testing applications and games which query for the memory budget adjusting their behavior accordingly.

They layer does not set a hard limit on the amount of VRAM thus applications can still make allocations even though the reported budget might indicate no memory is left, if the set limit is lower than of actually available VRAM.

I've added Copyright © 2017 Google Copyright © 2019 Red Hat since I initially just copied the other layers in Mesa to get the layer up and running and then added the VRAM limit functionality.