build: nix dev shell

[MrFoxPro]

This is my draft for devshell.

It includes:

• devenv: https://devenv.sh/reference/options
• edgedb-server bootstrapping (up command)
• treefmt tool to format whole codebase (alejandra for Nix, rustfmt and shellcheck)
• direnv's .envrc. You need to install https://direnv.net, so development shell will automatically load whenever you enter directory.

Here I probably needed maintainers assistance @scotttrinh , as I don't known your requirments for this project. If you're interested in this, I can help with configuring it further, we can get calls in edgedb discord, for example.

[aljazerzen]

I need something like this myself, I'd be up for merging it.

I would make it a bit less opinionated - we can use plain mkShell (or the one provided by crane) instead of devenv. direnv also does not need to be required, we can just add .gitignore entry and allow people who want it to set it up themselves.

@MrFoxPro can I take over this effort?

[aljazerzen]

I've published a separate repo for edgedb nix packages here: https://github.com/edgedb/packages-nix

I've also made this PR much less opinionated on tooling and provided only a plain nix shell with minimal tooling. Providing other tooling (such as formatters) is up to individual contributors.

[scotttrinh]

This looks good to me, thanks @MrFoxPro and @aljazerzen