* Support for Layer 2 networks with transaction fees on both layers
* Use variable name in transaction-breakdown
* Add comment on code source to ui/helpers/utils/optimism/fetchEstimatedL1Fee.js
* Fix unit tests
* Ensure values passed to are defined
* Fix activity log
* Upgrade style from Enzyme to React Testing Library
* Use real i18n provider instead of a fake one so that we can look for
English text instead of just i18n strings, improving readability
