fix: incoming transaction polling race condition

[matthewwalsh0]

Explanation

Prevent multiple simultaneous timeouts being created if stop and start are called while a previous asynchronous update is still in progress.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

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Note

Prevent duplicate timers and concurrent updates in IncomingTransactionHelper by tracking in-progress updates and clearing timeouts, with tests and changelog updated.

• Transaction polling (Incoming):
  • Update IncomingTransactionHelper to track in-progress updates with #isUpdating, preventing additional intervals from being queued while an update is running.
  • Clear any existing timeout before scheduling the next interval to avoid duplicate timers.
• Tests:
  • Add test ensuring repeated start/stop calls during an ongoing update only schedule one timeout and perform a single fetchTransactions call.
• Changelog:
  • Add Unreleased fix entry: prevent race condition causing excessive incoming transaction polling.

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