GH-598: changes driven from discoveries the debugging gave us

[bertllll]

[!NOTE] Adds accounting debug stats and message ID utilities, refactors pending-payables scanner and log wording, and updates address/test helpers.

• Logging/Debugging:
  • Introduce logging_utils with accounting_msgs_debug (aggregate per-address debits over a window) and msg_id_generator.
  • Wire into Accountant (logging_utils, DEFAULT_ACCOUNTING_MSG_LOG_WINDOW, debug containers); msg_id() now uses new generator.
• Accountant:
  • record_service_provided/consumed return u128; debug-posting collection for Report* handlers.
  • Improved trace/info wording for pending-payables reruns.
• PendingPayableScanner:
  • Split into start_scan.rs and finish_scan.rs.
  • Rename caches/wording from "suspected" to "supposed"; log "Collected … supposed failures".
  • Simplify harvesting/merging APIs (use vectors, no Option), and tidy emptiness checks.
• Tests/Strings:
  • Update expectations across tests and multinode integration to new log messages and behaviors.
  • Remove old MessageIdGenerator from sub_lib; add tests for new generator.
• Utils:
  • Change blockchain::test_utils::make_address layout; adjust expected addresses in tests accordingly.

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