feat: use OnceCell for Signed::hash

[klkvr]

Motivation

closes #1987

Lazily computes hash for the transaction in Signed. Methods relying on hash are now bounded by T: RlpEcdsaTx which works for all of the transactions we have but would likely get trickier for custom signature usecases

Solution

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

I like this,

we should make it very clear that this Signed type is specifically for transactions, it's already mentioned but I think we can make this even clearer

[DaniPopes]

Why can't we use std here?

[klkvr]

we can but we'd still need once_cell in no-std

[mattsse]

@klkvr we can simply upstream this to alloy:

https://github.com/paradigmxyz/reth/blob/b955551f8b3b37b0ead6862e8c1bdae1e7ff69e9/crates/primitives-traits/src/sync.rs#L3-L9

[klkvr]

We need Signed<TypedTransaction to still be usable as it seems that there are people relying on it e.g #2070

So this means we need to somehow have a helper tx_hash(&self, signature) -> B256 on it. RIght now it's only present on RlpEcdsaTx which has a transaction type AT which is irrelevant for TypedTransaction. For now I've extended SignableTransaction with a tx_hash_with_signature method doing the same thing

Also I've changed into_signed to have default impl using new_unhashed

[mattsse]

lgtm!

but blocking until we finalize #2138

[mattsse]

ah these we no longer need because part of SignableTransaction