CI snapshot testing

[jkelin]

Whenever I'm making changes to shared code, especially the compiler, I'm worried about breaking things. We have a bunch of examples, I propose we convert them to snapshot tests which render fist frame and verify that it matches the expected image. Then finally we should have these tests run in Github Actions on every commit/PR.

As an added bonus, they can verify that there are no Vulkan validation errors when running.

[leotmp]

That would be nice! Though there currently are validation errors on AMD, so some of them would fail already :). It's about using all those buffer usage flags together, i need to add an Allocation_Type parameter to mem_alloc.