refactor: bridge status polling into intent/bridge poller classes with shared lifecycle

[oscarwroche]

Explanation

• Extract shared polling lifecycle into BasePoller and split intent vs bridge logic into IntentTxPoller and
  BridgeTxPoller.
• Keep BridgeStatusController’s public API unchanged; #fetchBridgeTxStatus now delegates to the appropriate poller.
• Add focused tests to cover new poller paths, intent approval flow, and edge cases to preserve coverage.

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
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Introduces a shared polling framework and splits provider-specific logic.

• Extracts common lifecycle into BasePoller; adds BridgeTxPoller and IntentTxPoller with a normalized PollerContext and hooks (fetch, afterUpdate, onFinalStatus, onError).
• BridgeStatusController.#fetchBridgeTxStatus now delegates to the appropriate poller; removes inline intent/bridge status handling and related imports, preserving the public API.
• Pollers handle status updates, completion timing, attempts/backoff, event tracking, TC sync, and publishing destinationTransactionCompleted.
• Adds comprehensive tests: new utils/polling/*.test.ts, expanded intent flow tests (approval success/failure, history update failure), and bridge polling edge cases (missing srcTxHash, validation failures, featureId tracking skip, restart/stop polling semantics).
• Minor test harness updates (configurable approval status) and a guard to skip rekeying when pre-submission history is missing.

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