Remove T1 hardfork gating in transaction pool after T1 activation

[legion2002]

Context

In PR #2121, we added hardfork gating for expiring nonce transactions in the transaction pool:

• tt_2d_pool.rs:add_transaction() takes a TempoHardfork parameter to determine if expiring nonce transactions should be handled specially
• This is necessary during the transition period to correctly handle nonce_key == U256::MAX transactions

Task

Once T1 is active on all networks (mainnet, testnet), we can simplify the code:

1. Remove the hardfork parameter from AA2dPool::add_transaction()
2. Always treat nonce_key == U256::MAX as expiring nonce transactions
3. Remove the hardfork lookup in TempoTransactionPool::add_transaction()

Files to update

• crates/transaction-pool/src/tt_2d_pool.rs
• crates/transaction-pool/src/tempo_pool.rs

Related

• PR feat: expiring nonces #2121 (temporary/expiring nonces implementation)

[AlexWaker]

May I take this? If no one else has claimed it, I'd be happy to work on this task.

[AlexWaker]

PR #2237