Dispute-mon checks output roots against multiple rollup nodes

[pauldowman]

Dispute-mon takes multiple --rollup-rpc arguments, or one with a comma-separated list.

Implements logic described in https://github.com/ethereum-optimism/optimism/issues/11019, and keeps the assumption of assuming the output root was safe if safe head data isn't available.

Closes https://github.com/ethereum-optimism/optimism/issues/11019