Create empty `evm-shared` module

[alarso16]

To allow a "staging area" and immediate de-duplication of coreth and subnet-evm code, we could create a shared module with a mixture of adapted go-ethereum code and our code. Some quick notes:

Pros

• immediate code deduplication
• A "staging area" for moving into vms/evm to provide minimal refactoring for compilation

Some cons:

• Much of the duplicate code requires registering customtypes or params. We need some strategy for testing both options effectively without too large of a diff
• Slightly missing the point of aiming towards a single go.mod world
• Increases complexity of the codebase (more CI jobs, random packages in different module)

There should be some POC branch to see how it would work, but it may be more hassle than its worth