Immutable gas refunder

[shotaronowhere]

This immutable gas refunder is intended specifically as an optimization for the sequencer inbox. The immutable refunder is ~10k gas cheaper. Since the sequencer inbox now has a batch poster manager, the batch posters can change. To accommodate this, the immutable gas refunder no longer maintains a refundee allow list, only a single immutable allowed contract.

The other notable deviation from the mutable gas refunder is a small refactor of an event from

event RefundedGasCosts( address indexed refundee, address indexed contractAddress, bool indexed success, uint256 gas, uint256 gasPrice, uint256 amountPaid);

to

event SuccessfulRefundedGasCosts( uint256 gas, uint256 gasPrice, uint256 amountPaid);

and

event FailedRefundedGasCosts( uint256 gas, uint256 gasPrice, uint256 amountPaid);

which saves about 1000 gas.

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There are ideas to avoid using a gas refunder all together, but whilst we still use a gas refunder, atleast an immutable version will cut costs.