fix: remove OpCode enum and update VMOperation's op field type

[mouseless0x]

Motivation

Addresses #1902

Ensures that tracing with VmTrace enabled will continue to be future proof in the presence of any opcodes added/renamed when ethereum undergoes a new hardfork.

Solution

Removed the ethers::core::types::OpCode enum by deleting it's source file

Changed VMOperation's op field to be of type string.

Create new enum ExecutedInstruction that deserializes opcodes from VmTrace into either ExectutedInstruction::Known(Opcode) or ExecutedInstruction::Unknown(String)

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[mattsse]

imo this is probably easier to maintain than an enum, so I'm supportive of this,

[gakonst]

Should we instead do enum Opcode { Known(Opcode), Unknown(String)? I like the ability to match.

[mouseless0x]

Should we instead do enum Opcode { Known(Opcode), Unknown(String)? I like the ability to match.

This route looks like a valid solution to unwanted serialization errors - I will work on implementing it, and we can test how it works.

[mouseless0x]

Unsure whether it is necessary to test deserializing unknown opcodes, can remove the test if not needed

[gakonst]

typo on the type, lgtm otherwise

[mouseless0x]

Good catch, typo has been fixed

[mouseless0x]

forgot to add files to prev comment