Clean up data writers

[roberth]

Description of changes

These functions appear to have been added by mistake.

This change is the bare minimum to reduce maintenance.

Whether to further deprecate or document the aliases is still to be decided.

See #244835 (review) and subsequent comments.

• Remove duplicate implementations
• Deprecate makeDataWriter; not used in Nixpkgs and neither specific enough nor general enough
• Improve test, assuming we keep the aliases.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[Mic92]

First I was concerned this wouldn't pretty print formats, but it does. So looks good to me.

[Mic92]

writers.writeJSON still seems more ergonomic to use than (pkgs.format.json {}).generate.