Duplicate workflow IDs across pipelines' manifests don't raise errors

[emmeowzing]

They just overwrite each other. I think I should error on this and warn users to ensure there's no confusion. It's easy with this orb to start copying similar pipeline manifests, and just as easy to forget to update the pipeline's workflow IDs so they're now different.

[emmeowzing]

Duplicate orb aliases w/different orb version references should be errored on as well prior to merging configs. Otherwise it'll just take the last one and it'd be rather confusing why something was referencing only one of the versions in the generated config.