build: Use nix to manage dev tooling starting with clang-tidy

[jackgerrits]

Nix allows us to have a consistent developer environment. Perhaps the most useful instance of this is that the commands that are run locally use the exact same version of tooling as what is run in CI.

Documentation:

• How to install Nix
• How to use this tooling to format (not yet ready for consumption due to version change)
• How to use this tooling to run clang-tidy

All args are passed through to the underlying run-clang-format call.

To run clang-tidy on all files, as is done in CI you can run:

nix develop -c vw-clang-tidy

To just check specific files you can pass them as args:

nix develop -c vw-clang-tidy vowpalwabbit/core/src/kskip_ngram_transformer.cc

To apply fixes use -fix:

nix develop -c vw-clang-tidy vowpalwabbit/core/src/kskip_ngram_transformer.cc -fix

Using from Windows:

• Using WSL - commands are identical as above
• Using docker

  docker run -v %cd%:/src -it nixos/nix nix --extra-experimental-features nix-command --extra-experimental-features flakes develop /src -c vw-clang-tidy