Emit message hashes as an index event parameter

[rajivpo]

Makes me realize that we should emit the msg hash as an indexed event param.

Originally posted by @smartcontracts in #1107 (comment)

[smartcontracts]

For some context, these events should be bytes32 indexed msgHash instead of bytes32 msgHash. Will make finding the event much easier on the client-side:

optimism/packages/contracts/contracts/optimistic-ethereum/iOVM/bridge/messaging/iOVM_CrossDomainMessenger.sol

Lines 15 to 16 in cd1cfd4

	event RelayedMessage(bytes32 msgHash);
	event FailedRelayedMessage(bytes32 msgHash);

[smartcontracts]

If anyone wants to tackle this, please target the regenesis/0.5.0 branch (any changes to contracts go into regenesis/X.X.X branches, regenesis/0.5.0 is the next one that will be deployed).

[smartcontracts]

Fixed in OVM 2.0.