fix: implement overflow-safe per-byte gas multiplication

[sashass1315]

• Replace direct per-byte gas multiplications with an overflow-safe helper using bits.Mul64.
• Apply in Get, Set, and gasIterator.consumeSeekGas for key and value sizes.
• On overflow, pass math.MaxUint64 to GasMeter to trigger proper handling instead of silent wraparound.
• Keeps descriptors and existing gas semantics; prevents undercharging when GasConfig is customized.

[aljo242]

You should open an issue for tracking purposes of this work and detail what we gain etc for the change

this should be tested and have justification