fix: make get account proof retrieve latest known state

[juan518munoz]

As observed while updating the client with the latest node version, retrieval of account proof is prone to failure when the block number used for the request is different from the block where the last account update happened, as it returns a not found in those cases.

This PRs lighly refactors the logic of proof retrieval to return the account proof of an account up to the specified block.

[igamigo]

LGTM but I was also involved in investigating a fix for this so ideally @drahnr can take a look as well

[juan518munoz]

This PR as well as others are failing the MSRV check, attempted to fix it, to no avail.

[Mirko-von-Leipzig]

This PR as well as others are failing the MSRV check, attempted to fix it, to no avail.

Yeah we have some speculation going on in #1418 but its unclear at the moment wtf is going on there :)

[Mirko-von-Leipzig]

I'll leave @drahnr to formally approve, but LGTM.

Some suggestions on returning to the original phrasing and removing the changelog entry.

[Mirko-von-Leipzig]

I think this is a bit ambiguous and could mean that asking for block N could return data after N aka latest > N.

I think phrasing the entire comment as something like

// Optional block height at which to return the proof.
//
// Defaults to current chain tip if unspecified.

[drahnr]

The change is sound, thank you!

Note that #1394 will refactor the accounts table fully and introduce is_latest and address it that way.

I'd hence ask to undo all the documentation comments, to minimize my merge + rebase pains 🫠

[juan518munoz]

@drahnr rolled back most doc change in 0472580

[bobbinth]

Looks good! Thank you! I think we can ignore the MSRV check for this PR. I'll merge it as is.