Add better error handling to `opm`

[arewm]

We were trying to add a bundle to an index and were getting an error message

unrecognized type: string

using both the add and render commands. There should should be better error handling to make debugging of these issues easier.

This has been encountered multiple times. We traced down the suspected offending lines to when the spec.version was a string as well as when metadata.annotations.* were not strings, for example,

metadata:
  annotations:
    certified: true

Related issue in operator-sdk: operator-framework/operator-sdk#6168

[grokspawn]

Closing this one as completed. Please re-open if you continue to encounter this.