Nix packaging and infrastructure

[QuentinI]

Nix would solve or assist with solving packaging, development environment setup and reproducible builds for Iroha and accompanying WASM blobs.

This is a tracking issue for following sub-tasks (which are currently a rough plan and are subject to change)

• Provide a basic Nix flake for building Iroha and it's tools (Basic Nix flake #3415)
• Use Nix-controlled environment to build WASM blobs (Investigate using Nix-controlled environment to build WASM binaries #3416)
• Document basic usage of Nix-packaged Iroha
• Support cross-compilation with Nix (possibly blocked by [refactor]: Remove ursa dependency #3422)
• Provide a usable devShell

Some things that could be potentially done with a workable Nix infrastructure

• Use nix infrastructure in CI?
• Provide a NixOS module for deploying Iroha peer?
• Build Iroha Docker images with Nix?
• …