Implement RFC 0059: Standardized Dependency Metadata

[sophiewigmore]

We should implement Paketo RFC 0059 to standardize dependency metadata.

We should do this in a backwards-compatible manner, so buildpacks can move over to the new structure as they please, without breaking

This work will be important for unblocking ARM64/multi-architecture buildpack support, by enabling dependency metadata for architecture specific dependencies.

[loewenstein]

Should we explore if a separate package commonly used by packit and libpak would be feasible?

[loewenstein]

Also started a discussion on Slack about this to get broader feedback from all core devs.