lib/systems/inspect.nix: factor out toPretty

[ghost]

Description of changes

This commit factors out the pattern-list pretty printer added to check-meta.nix in #222852 so it can be used elsewhere.

It also disables (by default) multiline output and filters informationless entries like parsed={} before printing.

Sample output:

$ NIXPKGS_ALLOW_BROKEN=1 nix-instantiate . -A pkgsStatic.systemd
error: Package ‘systemd-253.1’ in /git/nixpkgs/pkgs/os-specific/linux/systemd/default.nix:743 is not available on the requested hostPlatform:
         hostPlatform.config = "x86_64-unknown-linux-musl"
         package.meta.platforms = [ "aarch64-linux" "armv5tel-linux" "armv6l-linux" "armv7a-linux" "armv7l-linux" "i686-linux" "m68k-linux" "microblaze-linux" "microblazeel-linux" "mipsel-linux" "mips64el-linux" "powerpc64-linux" "powerpc64le-linux" "riscv32-linux" "riscv64-linux" "s390-linux" "s390x-linux" "x86_64-linux" ]
         package.meta.badPlatforms = [ { isStatic = true; } ]
       , refusing to evaluate.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.05 Release Notes (or backporting 22.11 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.