* Implement last_checkpoint_storage_at
* Add reverted_storage_at for externalities
* sstore_clears_count -> sstore_clears_refund
* Implement eip1283 for evm
* Add eip1283Transition params
* evm: fix tests
* jsontests: fix test
* Return checkpoint index when creating
* Comply with spec Version II
* Fix docs
* Fix jsontests feature compile
* Address grumbles
* Fix no-checkpoint-entry case
* Remove unnecessary expect
* Add test for State::checkpoint_storage_at
* Add executive level test for eip1283
* Hard-code transaction_checkpoint_index to 0
* Fix jsontests
* Add tests for checkpoint discard/revert
* Require checkpoint to be empty for kill_account and commit
* Get code coverage
* Use saturating_add/saturating_sub
* Fix issues in insert_cache
* Clear the state again
* Fix original_storage_at
* Early return for empty RLP trie storage
* Update comments
* Fix borrow_mut issue
* Simplify checkpoint_storage_at if branches
* Better commenting for gas handling code
* Address naming grumbles
* More tests
* Fix an issue in overwrite_with
* Add another test
* Fix comment
* Remove unnecessary bracket
* Move orig to inner if
* Remove test coverage for this PR
* Add tests for executive original value
* Add warn! for an unreachable cause
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