CLI: Support validations with references to other build info dirs

[ericglau]

Users may want to validate storage layout compatibility between contracts in different versions (branches or tags) of a repo. Each distinct version may have its own build-info dir.

Consider supporting multiple build-info dirs, and allow the --reference parameter or @custom:oz-upgrades-from annotation to specify the specific build-info dir as a further qualifier.

Originally requested in https://forum.openzeppelin.com/t/storage-layout-verification-on-complex-projects/40773