Overhaul build system once and for all

[youwen5]

Hopefully the last PR needed to fix the tooling so that I can actually run the code.

Dejankify build system so that it does not rely on hardcoded system paths, actually works on other computers, and provides reproducible builds.

• Use Meson instead of CMake
• Use ninja instead of Make
• Package liboai library and provide it using Nix
• Improve development experience
• Add Git hooks to enforce formatting
• Add CI checks for formatting