[Performance + VRAM] Re-implement 16-byte Vertex Format + use 4 Byte alignment

[thr3343]

The 16-Byte vertex format for terrain was planned in earlier versions of VulkanMod, but was scrapped due to causing performance regressions on AMD's GCN architecture

This patch exploits a workaround by doubling the vertex byte alignment to 4 bytes instead of 2, which fixes the regression and allows the 16-byte format to be used on GCN at full performance.

The 16-Byte vertex format provides the following advantages over the current 20-byte format

• VRAM usage reduced by 20%
• Reduced bandwidth usage when loading/updating Chunks
• FPS + Performance improvements on some hardware (e.g. Nvidia Turing or later)