smite-ir: add malformation parameter to funding_created

[NishantBansal2003]

ref: #178

Depends-on: #212

Add a malformation parameter to SendFundingCreated that overwrites an allowlisted field of funding_created before sending it to the target. Some fields currently only contain valid values, so this allows the IR to exercise their invalid values as well.

Oracle state is updated based on the message actually sent to the target, after applying the malformation. If the malformed signature cannot be decoded, we send only the invalid signature without marking the state as desynced, since the target should simply reject it as an invalid signature rather than behave differently.

The generator produces only non-malformed funding_created messages, OperationParamMutator adds malformations using repeated bytes, random bytes, or interesting integers matching the field's exact width.