Payer Report Verification

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When a PayerReport has been published on-chain, all the nodes should verify it and attest if valid.

Each node has the messages originated in the node which published the report, the timestampts, and congestion fees. The algorithm to verify a Payer Report should come to the same conclusion when running in different nodes: Payer X' used Y' credits. Payer X' used Y' credits, etc.