GH-598: Payments Revamp: Minimal Viable Product

[bertllll]

A brief explanation of how it works, plus some instructions for testing in the attached file: Payment mechanism testing guidlines.txt

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[!NOTE] Revamps the payments pipeline by replacing pending payables with sent/failed records, adding receipt/status processing and DB migration, overhauling blockchain submission/pricing, updating schedulers/config, and reworking errors, defaults, and tests.

• Payments/Data Model:
  • Replace pending_payable with new sent_payable and failed_payable tables; add migration 11→12 to create/drop accordingly.
  • Introduce explicit tx status tracking (pending/succeeded/reverted) and validation history.
• Accounting/Scanners:
  • Add pending_payable_scanner with tx_receipt_interpreter and rich utils (caching, result composition, retry hints).
  • Rework scan schedulers and receivable scanner modules.
• Blockchain Layer:
  • Overhaul bridge/agent/interface: price templates (new/retry), submit batches, map RPC/internal errors, and return structured receipt/status results.
  • Add chain-aware default scan intervals.
• Config/Bootstrap:
  • Replace suppress_initial_scans with automatic_scans_enabled; adjust CLI validation and defaults.
• Error & Status Modeling:
  • Add AppRpcError/InternalError and ValidationStatus with serde support; remove legacy types.
• Tests/Utils:
  • Extensive test updates; new recorder counter-messages, serializer mocks, and helpers.

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