Make more specific verification outcomes for GovernanceState

[shd]

Currently a large portion of the verification outcomes are put into Unclassified error. Errors need to be more specific.

What possible improvements at this point are visible:

• Cover all error messages from validation.rs
• Create additional 'InternalError' outcome and put all non-verification errors into that category
• In particular, (a) analyze duplicate governance procedure proposal and make it an InternalError; (b) communication problem error messages also can be put there.