tests.nixpkgs-check-by-name: Intermediate refactor

This prepares the code base for the removal of the `--version` flag, to
be replaced with a flag that can specify a base version to compare the
main Nixpkgs against, in order to have gradual transitions to stricter
checks.

This refactoring does:
- Introduce the `version` module that can house the logic to increase
  strictness, with a `version::Nixpkgs` struct that contains the
  strictness conformity of a single Nixpkgs version
- Make the check return `version::Nixpkgs`
- Handle the behavior of the still-existing `--version` flag with `version::Nixpkgs`
- Introduce an intermediate `process` function to handle the top-level
  logic, especially useful in the next commit

0 files changed, 0 insertions, 0 deletions