Add support for architecture selection during updating of buildpack dependencies

[dmikusa]

Summary

The update-buildpack-dependency too doesn't match correctly with the introduction of dependency architectures. This includes architecture as a consideration when filtering the dependencies to pick what is updated. A dependency now needs to match both the ID and ARCH.

This is presently pulling the architecture from the PURL as it's the only currently reliable spot to get it. In the future, when all of the buildpacks have switched to it, we should pull from the arch field.

Use Cases

Multi-arch support.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).