core/std library cleanup #1189
Description
core shouldn't contain anything evm-specific. It should only contain things that are truly "core" to the language and the compiler, along with some common abstractions.
std can contain evm stuff. It should be laid out in a reasonable way, eg evm ops live in std::evm::ops, and we shouldn't expose everything at the top level (no pub use evm::ops::* at the top level).