Implements ethereum/go-ethereum PR #31202 and #31618.
When local tracking is enabled:
- EthAPIBackend.SendTx tracks transactions after pool submission and keeps tracking temporary rejects so they can be retried by the local tracker.
- TxPool.AddLocal tracks accepted submissions and temporary rejects for local re-journal/re-submit flows, while preserving the original txpool error return to the caller.
This avoids persisting permanently invalid transactions while preserving retry signals for transient failures without masking submission outcomes in caller workflows.
Also included:
- classify temporary rejection reasons in core/txpool/locals
- expose SubPool.ValidateTxBasics and align LegacyPool implementation
- split low-tip rejection into ErrTxGasPriceTooLow
- simplify local tracker integration in txpool
- update txpool and eth tests for accepted vs retryable local tracking behavior
Refs: ethereum/go-ethereum#31202
Refs: ethereum/go-ethereum#31618
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