Get rid of the EVM and Contract Extension classes

[kantagara]

Summary
I've seen on Discord that a LOT of people are using the EVM class. Which for all the previous versions of our sdk is fine, but now we need to enforce people to use the ABI<-> C# contract builder in our upcoming release, so we need to remove the EVM class. (They'd still be able to build the contract themselves obviously).

Motivation
Removing them will leave a streamlined process for using the SDK.

Acceptance Criteria

• EVM and ContractExtension classes shouldn't be in the SDK.