Nix rework

[bladyjoker]

Relates to #636

A small as possible set of changes that introduces modular configurations via build.nix files (opt in) and a repo wide set of source checks that can be ran with nix fmt command.

That's my take on the current Nix best practices that I found to be empowering even to the Nix uninitiated.

DONE

• Enable flake-parts based Nix layout using "build.nix" files
  • https://flake.parts/
  • No real changes to the produced flake, it's just a wiring change
• pre-commit hooks using git-hooks.nix
  • Enable Nix checkers
  • Enable Haskell checkers (fourmolu 0.19.0.1, HLint v3.10)
  • Enable Markdown checkers
    • Tried but too many hits, perhaps it makes sense to gradually introduce with an allow list
  • Enable Rust checkers (clippy, rustfmt)
    • Too invasive and too many errors
  • Enable Python checkers (black, ruff)
  • Enable Shell checkers (shellcheck)
    • Great tool, but needs further config to ignore many generated shell scripts

BREAKING

• .github/workflows/simulation.yaml was using Fourmolu 0.15 I updated it to newer Fourmolu 0.19.0.1
• hydraJobs have been transposed, instead of hydraJobs.${system}.packages.foo now it hydraJobs.packages.foo.${system}

INSPECT

$ nix repl
Welcome to Nix 2.18.8. Type :? for help.

nix-repl> :lf .
Added 27 variables.

nix-repl> devShells.x86_64-linux.<TAB>
devShells.x86_64-linux.default        devShells.x86_64-linux.dev-top-level  devShells.x86_64-linux.web

nix-repl> checks.x86_64-linux.    
checks.x86_64-linux.ols-test             checks.x86_64-linux.pre-commit           checks.x86_64-linux.test-trace-verifier

nix-repl> packages.x86_64-linux.<TAB>
packages.x86_64-linux.agdaIOGPrelude               packages.x86_64-linux.agdaTraceParser              packages.x86_64-linux.linear-leios-trace-verifier  packages.x86_64-linux.short-leios-trace-verifier
packages.x86_64-linux.agdaLeiosSpec                packages.x86_64-linux.agdaWithDeps                 packages.x86_64-linux.networkSpec                  packages.x86_64-linux.simRealism
packages.x86_64-linux.agdaSets                     packages.x86_64-linux.combined-haddock             packages.x86_64-linux.ols                          packages.x86_64-linux.test-trace-verifier
packages.x86_64-linux.agdaStdlib                   packages.x86_64-linux.hsTraceParser                packages.x86_64-linux.ols-test
packages.x86_64-linux.agdaStdlibClasses            packages.x86_64-linux.leios-trace-processor        packages.x86_64-linux.pre-commit-check
packages.x86_64-linux.agdaStdlibMeta               packages.x86_64-linux.leiosDesignPdf               packages.x86_64-linux.read-the-docs-site

nix-repl> hydraJobs.<TAB>
hydraJobs.checks     hydraJobs.devShells  hydraJobs.packages