Vulkan improvements 1

[ksuprynowicz]

This should improve performance and compatibility due to uniform buffers having proper alignment now.

[ada-tv]

UI now works properly on my system. The desktop HUD doesn't use the premul-alpha hack shader DrawTexturePremultipliedSRGBToLinear on the Vulkan display plugin, so it has dark borders. See display-plugins/OpenGLDisplayPlugin.cpp:416

I tried messing with the resolution scale, and found something really weird:

This is what's rendered after starting with 0.4 scale. This feels like it might be bad viewport bounds, since the visible part is the top-left corner of the framebuffer.

That hunch seems more likely with this, which happens when scaling the resolution down from 1.

With the lower res scale, I also noticed that the framebuffer is using wrapping instead of clamping on both renderers. (there's a line of green pixels at the top, which is my avatar's clothes) See #1951, where the OpenGL backend also incorrectly does this, but only on the forward renderer for whatever reason.