[Feature] Implement Encodable and Decodable for OpTxType

[ozgunozerk]

Component

consensus

Describe the feature you would like

Right now, OpTxType does not derive these.

And RlpEncodable and RlpDecodable cannot be used on enums.

Might be useful and easier for other projects that are using these. For example: paradigmxyz/reth#12443

Additional context

I can volunteer to take on this issue, however a bit of guidance and context would be appreciated.

Why RlpEncodable and RlpDecodable designed in a way that they only support structs but not enums?

Does it make sense to extend the supported set for these macros so that they can support enums? Or should we implement the Encodable and Decodable traits manually?