`opm validate` does not require 'catalog metadata' used for operator discovery

[grokspawn]

opm validate historically has performed schema validation only, meaning that it verifies that an FBC blob can be converted to the internal storage format.

This has led to some unfortunate discoveries when we updated our CSV metadata format from olm.bundle.object base64-encoded to a structured olm.csv.metadata and encountered dependencies some teams had on the format.

In general, though OLM does not require this metadata to function, its expression is part of our API and should be considered part of the tool's responsibility.