Support robust consensus strategies between providers

[gregorydemay]

Whenever the EVM-RPC canister queries multiple providers, equality between all responses are expected, otherwise all individual results are returned in the Inconsistent variant. This means that as soon as provider is for example offline, all results will be deemed Inconsistent. A more robust approach would let the caller specify a k-out-n threshold, so that equality of at least k (non-error) responses among the n providers queried is sufficient to have consensus.