test: zswap event subscription tests

[mariyade]

Summary:

• added Zswap ledger event subscription coverage in integration and e2e tests
• validated correct ordering between Zswap events and the subsequent DustSpendProcessed event after shielded transaction
• improved logging in Dust ledger event collection function for better debugging
• updated Dust ledger event subscription tests to validate ledger order rather than contiguous order
• increased timeout in subscribeToUnshieldedTransactionEvents from 500ms → 5000ms to reduce flakiness
• added validation for shielded transactions to confirm no unshielded outputs or fees are exposed
• re-enabled the 'dust-queries.test' test following completion of PM-20789

[THErealARETE]

1. Good Test Coverage: Comprehensive integration and e2e tests for zswap subscriptions
2. Clear Documentation: Test descriptions follow Given/When/Then format with good comments
3. Consistent Patterns: Zswap utilities follow the same pattern as dust utilities
4. Ordering Validation: Proper validation of event ordering between Zswap and Dust events
5. Improved Logging: Added debug logging for better debugging capabilities
6. Proper Cleanup: Tests properly unsubscribe and close connections
7. Good Refactoring: Renaming dust-utils.ts to dust-ledger-utils.ts clarifies purpose