Ensure compatibility of misbehaviour evidence JSON serialization with CometBFT v0.37.10 and v0.38.11

[romac]

In CometBFT v0.37.10 and v0.38.11, the name of the fields of the DuplicateVoteEvidence and LightClientAttackEvidence structs when serialized to JSON have changed from PascalCase to snake_case.

As Hermes uses those structs to process and report misbehaviour evidence, we should make sure that we can still do so with those versions using snake_case, while keeping backward compatibility with chains running previous versions using UpperCamelCase.