VoteTx should fetch all the voter delegations on wasm

[Fraccaman]

Right now, the vote_proposal tx is expecting from the client a list of validators for which the voter has a delegation to. The Governance VP is then validating the list, but the validation logic is redundant and not optimal. We should instead fetch the voter delegation list directly from the wasm transactions.

[Fraccaman]

@brentstone it would come real handy if we could easily fetch the set of validator addresses for a specific delegator

[brentstone]

If I recall correctly, there is a dependency issue between proof-of-stake and governance here that would possibly require a refactor.