Add TransactionManager to handle stalled tx

[evgeny-stakewise]

Summary

Routes all wallet transactions through a single TransactionManager.transact(...) path and removes transaction_gas_wrapper. The manager owns submit + receipt-wait under a lock (one in-flight tx at a time), reuses the lowest unconfirmed nonce, and replaces a stuck pending tx with bumped fees instead of an in-call retry loop.

What changed

• transact(tx_function, tx_params=None, high_priority=False) -> TxReceipt | None: serializes submit and the receipt wait so exactly one wallet tx is in flight at a time; returns the receipt (or None on revert).
• Two gas strategies:
  • high_priority=True (e.g. validator registration) skips the default-gas attempts and submits high-priority fees straight away.
  • high_priority=False keeps the existing default-gas attempts loop, escalating to high-priority fees on FeeTooLow.
• No in-call fee-bump loop. A run submits once; if it doesn't confirm within execution_transaction_timeout the task retries on its next run, where a pending tx is detected and its fees bumped (max(high_priority, bump(prev)), capped at max_fee_per_gas).
• Deleted transaction_gas_wrapper; migrated every caller (validators register/fund/consolidate, withdrawals, exits, harvest, reward splitter, meta vault) plus the tx_aggregate / deposit_to_sub_vaults wrappers, which now return TxReceipt | None.

Behavior note

• A receipt timeout is caught inside the manager: transact returns None and leaves the tx pending, so the next run detects and replaces it (previously TimeExhausted propagated out of the caller).
• When the pending tx is at or near the max_fee_per_gas ceiling, the bump can't clear the node's +10% replacement threshold, so the manager skips the replacement, logs a warning, and returns None instead of broadcasting a doomed underpriced tx — it mines once the base fee drops or is retried on a later run.