astc: General changes and optimizations

vk_rasterizer: Implement scissor clears and layered clears

maxwell_to_vk: Implement RG32 and RGB32 integer vertex formats

gl_shader_decompiler: Add layer component to texelFetch

renderer_opengl: Detect Nvidia Nsight as a debugging tool

Use getenv to detect Nsight.

vk_rasterizer: Fix vertex range assert

video_core: Implement RGBA16_SNORM

shader_decode: Reimplement BFE instructions

maxwell_to_vk: add vertex format eA2B10G10R10UnormPack32

renderer_opengl: Keep frames synchronized when using a GPU debugger.

vk_shader_decompiler: fix linux build

End can be equal to start in CalculateVertexArraysSize. This is quite
common when the vertex size is zero.

- Fixes renderdoc with OpenGL renderer.

PageTable: move backing addresses to a children class as the CPU page table does not need them.

texture_cache: Report incompatible textures as black

texture_cache/surface_params: Force depth=1 on 2D textures

video_core: Initial implementation of transform feedbacks

This PR aims to reduce the memory usage in the CPU page table by moving
GPU specific parameters into a child class. This saves 1Gb of Memory for
most games.