Allow to publish packages with test dependencies not in the registry

[fsoikin]

Description of the change

The primary motivation for this is allowing circular dependencies between packages for testing only. In this scenario one of the packages is added to extra_packages section of the other with a patched dependencies property. For example:

# github/collegevine/purescript-elmish/spago.yaml
workspace:
  extra_packages:
    elmish-testing-library:
      repo: https://github.com/collegevine/purescript-elmish-testing-library.git
      version: v2.0.0
      dependencies: [] # <-- no Elmish in dependencies, avoiding the cycle

package:
  name: purescript-elmish
  dependencies: ...
  test:
    main: ...
    dependencies: ["elmish-testing-library"]

This scenario was actually working fine for the most part, and the only obstacle was publishing the package. Because the extra_packages dependency is not in the package registry, Spago refuses to publish. This change makes it so that Spago will only apply this rule to "core" dependencies, but not to "test" ones. See also this Discord discussion.

To achieve this, the following changes have been made:

• Fetch.run no longer returns a single list of dependencies for every package, but instead returns them in two buckets - "core" and "test".
• The lockfile format has been changed to support the same structure:
  • from: { dependencies, build_plan, test_dependencies }
  • to: { core: { dependencies, build_plan }, test: { dependencies, build_plan } }
• Most call sites of Fetch.run ultimately call toAllDependencies, which flattens the whole tree and combines core with test.
• Publish.run specifically picks only core and drops test, so as not to perform all the rigorous checks for the test dependencies.
• Build.getBuildGlobs no longer adds test globs (i.e. test/**/*.purs) for all workspace packages, but only for the "selected" ones. This is because only "selected" packages will have their test dependencies added to the build plan.

Checklist:

• Added the change to the "Unreleased" section of the changelog
• [ ] Added some example of the new feature to the README
• Added a test for the contribution (if applicable)

[f-f]

Brilliant refactoring of the new caching code in Fetch - @finnhodgkin could you test this code to see if the perf still holds up?

[f-f]

Stellar work! Thanks 👏

[fsoikin]

Awesome! Could you cut a new version soon so I can use it to publish spec?

[f-f]

Yeah I will merge #1275 now then cut a new version!

[f-f]

@fsoikin 0.93.39 is out 🚀