Switch LazyTransaction gas caps from *big.Int to *uint256.Int and convert once at pending retrieval time.
In miner ordering, keep fee comparisons on uint256 and precompute TRC21 gas price in uint256 form to avoid repeated big-int conversions in heap comparisons.
Also update affected tests and call sites in legacypool/worker/helper paths.
Compatibility: LazyTransaction exported field types changed (GasFeeCap/GasTipCap).