Adds fraud prover code

[CAPtheorem]

Adds the fraud-prover service

CAUTION - the fraud prover does not currently work - it's able to detect fraud, but currently unable to correctly _initializeFraudVerification, so that and all downstream steps fail.

Specifically, the fraud prover triggers a revert at VM Exception while processing transaction: revert Pre-state root global index must equal to the transaction root global index in OVM_FraudVerifier.sol line 134:

require (
            _preStateRootBatchHeader.prevTotalElements + _preStateRootProof.index + 1 == _transactionBatchHeader.prevTotalElements + _transactionProof.index,
            "Pre-state root global index must equal to the transaction root global index."
        );

This issue may be related to (1) injecting fraud via the Batch_submitter, and more generally, (2) fraud proving and correction in the setting of batch submissions, rather than unitary test submissions.

ToDo: The fraud prover currently is brittle, in the sense that it fails silently for many error conditions and e.g. empty returns. There are also many issues relating to indexing of various data structures, especially for batch transactions.

[codecov-commenter]

Codecov Report

Merging #19 (d77f794) into develop (679ee38) will not change coverage.
The diff coverage is n/a.

❗ Current head d77f794 differs from pull request most recent head 164ced8. Consider uploading reports for the commit 164ced8 to get more accurate results

@@           Coverage Diff            @@
##           develop      #19   +/-   ##
========================================
  Coverage    82.21%   82.21%           
========================================
  Files           48       48           
  Lines         1895     1895           
  Branches       303      303           
========================================
  Hits          1558     1558           
  Misses         337      337           

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[InoMurko]

Great work, but can we add some CI integration and enable continuous testing?