fix(consensus): populate chain id when decoding signed legacy txs

[Evalir]

Motivation

The chain id was not being populated when decoding a signed legacy tx, leading to decoding issues.

Closes #125

Solution

Populate the chain id param when decoding.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

I'm a bit confused why TxLegacy is also Encodeable and Decodeable,

this can be misused easily, because that's most likely never what you want?

re signature and eip155:

https://github.com/paradigmxyz/reth/blob/77f38574e20d2871c7e38cf99fae2fc5cd1cee02/crates/primitives/src/transaction/signature.rs#L98-L98

[Evalir]

@mattsse agreed it feels a bit odd to have TxLegacy as encodable/decodable, but I think we should not include removing that in this PR as this is a bugfix for the signed decoding case Signed<TxLegacy>. Let's add a separate issue for this and fix in a new PR

[mattsse]

last nit