Expose pubkey of remote validators

[ethanfrey]

ConsumerPacket::AddValidator requires the tendermint pubkey, and we will need that information to implement slashing. However, that information is not available in the CosmWasm queries we have access to.

We need to provide said information to the converter contract somehow.

[maurolacy]

This is not needed in the end, because we either trust the Consumer blockchain misbehaviour events without verifying them (V1), or will verify the misbehaviours using an approach similar to ICS (V2), in which the offending validator pubkey is included as part of the evidence.

Will document this better, and close it.