* op-challenger: Tidy up TxSender

Don't return receipts as they always ignored
Return an error when a transaction publishes but reverts rather than logging and ignoring
Add a method that returns errors for each individual transaction

* op-challenger: Simulate ClaimCredit transaction before sending actual transaction

Detects when credit is reported as available but is actually still locked by the DelayedWETH contract.

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Co-authored-by: refcell <abigger87@gmail.com>