fuzz & differential testing of system config update event log handling

[roberto-bayardo]

Requested followup to https://github.com/ethereum-optimism/optimism/pull/8785

We should break out the deserialization logic for log event handling into a public handler function and then import those handlers into our solidity differential-testing and use vm.getRecordedLogs in a fuzz test to differentially test the handlers themselves.

Additional context

[BlocksOnAChain]

@roberto-bayardo what are the future steps for this issue and is it still relevant for you to work on? CC: @sebastianst @tynes for visibility and ideas.