Default value of the state's Account should a represent non-existent account

[Wollac]

Component

consensus, eips, genesis

What version of Alloy are you on?

alloy-consensus v0.3.6

Operating System

None

Describe the bug

Currently, alloy_consensus::Account uses derive to implement Default. This leads to some arbitrary values, e.g. code_hash of 0x00 does not correspond to the hash of any contract code.
To be able to use the default value as the actual value of a missing account, and to be consistent with other types in alloy_consensus (like Header), it should contain a custom implementation of an actual valid (empty) account.