change flake refs and update flake.lock(s)

[Gerg-L]

All the lockfiles of the templates were from late 2022
the nixpkgs flake refs were using the master branch and had a comment recommending using the flake registry
updated all instances of nodejs-18_x to nodejs_18

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[Gerg-L]

I don't know why there is locks on any of the template flakes at al...

[lucperkins]

@Gerg-L In general, I like having flake.locks in the template because it eliminates one potential source of breakage. I want people to be able to nix init -t and get to work without worrying that upstream flakes will introduce breaking changes. In fact, one of the reasons we created FlakeHub and are nudging the community toward SemVer is precisely to make things like this less of an update-and-cross-your-fingers scenario.

But I clearly haven't been all that vigilant about updating these, so I appreciate the help 😄 I'll see if maybe there's a way to automate this in the future. For now, LGTM.