Deduplicates callback definitions and situates it in one place.

Deduplicates a lot of long callback declarations

Deduplicates really long std::function declarations to make the
interface nicer to read.

cmake: prefer system libraries

Vulkan: Implement Alpha coverage

service_thread: fix uninitialized memory usage

hle: service: audio: Use default service thread.

 Configuration: Add per-game input profiles 

vulkan_common: promote extension usages to core when possible

yuzu-cmd: link SDL2 correctly

externals: don't install xbyak as part of yuzu install

externals: update dynarmic, SDL2

Prevent yuzu from trying to install bundled xbyak as it'd likely
conflict with system xbyak package.

Error: Orphaned: include/xbyak/xbyak.h
Error: Orphaned: include/xbyak/xbyak_bin2hex.h
Error: Orphaned: include/xbyak/xbyak_mnemonic.h
Error: Orphaned: include/xbyak/xbyak_util.h
Error: Orphaned: lib/cmake/xbyak/xbyak-config-version.cmake
Error: Orphaned: lib/cmake/xbyak/xbyak-config.cmake
Error: Orphaned: lib/cmake/xbyak/xbyak-targets.cmake

video_core: add null backend

CMake: Use precompiled headers to improve compile times

general: fix compile for Apple Clang

video_core: Fine tuning the index drawing judgment logic

Vulkan: update initialization

shader_recompiler: add gl_Layer translation GS for older hardware

service: nifm: Update stubs for Submit/GetRequestState/GetResult

CMake: Fix FFmpeg find module

Explicitly use the bundled FFmpeg version, since we were auto-choosing
it before.