Fix `Exp`'s arithmetic `eval` when result exceeds `2^256`

[acuarica]

Similar case as https://github.com/acuarica/evm/pull/127 but for Exp's eval.

[github-actions[bot]]

size-limit report 📦

Path	Size
dist/sevm.js	17.29 KB (0%)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.14%. Comparing base (c7256fc) to head (cde5222).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #128 +/- ## ======================================= Coverage 94.13% 94.14% ======================================= Files 23 23 Lines 5354 5362 +8 Branches 931 931 ======================================= + Hits 5040 5048 +8 Misses 299 299 Partials 15 15 ```

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