twoliter: allow partial lockfile validation in some scenarios

[cbgbt]

Description of changes:

    twoliter: allow partial lockfile validation in some scenarios

    In some CI scenarios, it's useful to drop previously-built variant
    images into a Twoliter project's build directory and use Twoliter to
    publish those variant images.

    In these cases, Kit dependencies are not necessary, and it can be useful
    to avoid resolving them and comparing them against Twoliter.lock.

    This change allows skipping Kit lockfile verification only when
    executing certain `twoliter make` targets.

Testing done:

• All provided tests pass

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[cbgbt]

Sorry for the churn. I have another TL interface change I'd like to make. I can save it for a subsequent PR, though.

[cbgbt]

I disabled some additional, unnecessary artifact fetching. Some make targets needlessly requested workspace sources as an artifact of previously being part of the monorepo.

I need to test that specific change a bit more before merging, though.

[cbgbt]

Commenting so that GitHub will provide a useful comparison view.

[cbgbt]

^ addresses feedback from @bcressey

[sumukhballal]

LGTM! 👍

[cbgbt]

Force push to remove erroneous println!

[cbgbt]

build and default are effectively aliases to build-variant and are used in the bottlerocket repo. These targets now require kit verification.

[cbgbt]

^ rebase (without changes) on to develop

[cbgbt]

^ make changes to work with #357

[cbgbt]

^ force push because I missed build-all 😅