Prefer latest added bytecode in ContractsIdentifier when the match is not exact

[fvictorio]

If we lookup a contract using its bytecode and we get an exact match, then it's clear that we should use that contract.

Sometimes, though, we can get several partial matches with the same length. This is especially likely if the matches diverge only in the trailing metadata.

How this will actually be implemented in practice depends on how the codebase is modeled and the relationship of that model with the contracts identifier.