ICS02/ICS26: Evidence module integration for Equivocation

[mossid]

Misbehaviour predicate under ICS02 should handle equivocation(doublesigning) for tendermint headers.

The implementation will have the following interface

type ConsensusState interface {
...
  Misbehaviour(evidence.Evidence) bool
...
}

Misbehaviour must be a pure function, and the evidence related to the misbehaviour should be passed as the argument.

Each of the Evidence type will be defined under the concrete implementations of ICS02. For Tendermint, it will be defined under ibc/02-client/tendermint, initially including only the EquivocationEvidence. Unlike the normal tendermint.DuplicateVoteEvidence, it should be submitted only if more than 2/3 of the validator set double signs.

The IBC module will implement an evidence.Handler which route the infractions to appropriate ConsensusState.Misbehaviour, implementing handleClientMisbehaviour under ICS26. The end user will submit evidence.MsgSubmitInfraction to invoke the function.

This issue replaces [^1] in #4723

[fedekunze]

Note: this is a blocker for #4516

[fedekunze]

misbehavior for Tendermint was implemented on #5258. Closing