Incomplete validation for MsgRollappFraudProposal

[omritoptix]

In x/rollapp/types/message_fraud_proposal.go:14-32, the ValidateBasic method of the MsgRollappFraudProposal is incomplete. It does not validate fields such as RollappId, RollappRevision, FraudHeight, and PunishSequencerAddress to ensure they are correctly set and valid.
Without these validations, an invalid fraud proposal could be accepted for voting, run the full proposal lifecycle, only to fail during execution. This creates inefficiencies and risks undermining the governance process.