Create ADR for Cryptographic Verification of Equivocation

[sainoe]

Problem

The design of the ICS misbehaviour handling incorporates elements from both IBC and CometBFT logic to address Light Client Attacks. It is important to ensure that the wiring of these components remains consistent with the new requirements and assumptions introduced by this design.

Below are listed the main components of the design that need to be reviewed:

• Expect the IBC misbehaviour message to contain a Common Header - ref1, ref2
• Follow the logic in CometBFT to construct Light Client Attack Evidence - ref
• Use the IBC misbehaviour/LCA validation and consequently jail and tombstone validators for a time violation - ref
• Freeze an IBC light client under a valid misbehaviour/LCA reception - ref

Closing criteria

Address each item and integrate the resulting decisions to the ongoing ADR-005.

[sainoe]

Summarizing our last discussion with @ancazamfir @mpoke @romac @MSalopek, upon receiving a ICS misbehaviour message, the provider should be updated to:

• Not freeze consumer IBC client
• Verify that the consumer IBC client isn't Expired or return an error
• Ensure that it jails and tombstones validators only for standalone Cosmos chain infraction.

Accordinlgy, the Hermes misbehaviour handling logic should be updated to:

• Send both ICS and IBC misbehaviour msgs after detecting a LCA

Additionaly, we still need to clarifify if time violations should be considered as valid standalone Cosmos chain infractions.