tests.trivial-builders.references: refactor and move expressions into trivial-builders/test/references

[ShamrockLee]

Description of changes

Make a testScriptBin that contains the substituted test script.

• Add an installCheckPhase to check the result script with ShellCheck.
• Passthru as references.testScriptBin to run the (substituted) test script directly (without VM).
• Drop the logic in build script that detects if it is run in the Nix sandbox.
• Inline sample application; drop invoke-*.nix.

Format expressions.

• Format with nixpkgs-fmt.
• Use multi-line style of set patterns.

Call the samples with callPackage.

• Rename sample to samples.
• Take individual packages / build helpers directly from the set pattern.
• Define cleanSamples to filter out overriders such as <pkg>.override added by callPackage.

Passthru samples and invocation results for easier debugging.

• Passthru samples, references and directReferences

Move all the related files into directory trivial-builders/test/reference

• Make the trivial-builders/test directory cleaner, and samples.nix not ambiguous.
• Call it with callPackage ./references { } instead of callPackaeg ./references.nix in trivial-builders/test/default.nix.
• Pass it into tests.trivial-builders.writeStringReferencesToFile

Cc: @roberth

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
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[ShamrockLee]

Rebase onto the master branch.

[roberth]

This looks alright!

[roberth]

It works. Thanks!