Update SSTORE2 Library to be EOF-compliant (see EIP 3540)

[jakerockland]

Given that this sstore2 library was one of the initial reference points for the BytecodeStorage library that we developed at Art Blocks, I wanted to file this issue as a similar issue to mirror the one on our end (https://github.com/ArtBlocks/artblocks-contracts/issues/422) for increased visibility for the maintainers of this library as to how it may be impacted by EIP 3540.

cc @ryley-o