refactor(agglayer): refactor EthAddress and EthAddressFormat

[partylikeits1983]

Closes #2357

Description

The previous EthAddressFormat type served dual purposes: representing both real Ethereum addresses (e.g., origin token contract addresses, bridge-out destinations) and Miden AccountId values encoded in the 20-byte Ethereum address format (bridge-in destinations). This PR separates these concerns into two distinct types:

• EthAddressFormat (previously EthAddress) — A plain 20-byte Ethereum address. Used for origin token addresses, bridge-out destination addresses, and any context requiring a real EVM address. Provides new(), from_hex(), as_bytes(), into_bytes(), to_hex(), and to_elements().

• EthAccountIdFormat (previously EthAddressFormat) — A newtype around EthAddressFormat for the bridge-in (CLAIM) flow, where a Miden AccountId is encoded as [0, 0, 0, prefix, suffix]. Adds from_account_id() and to_account_id() conversion methods. Converts to/from EthAddressFormat via From impls.

Breaking Changes

• EthAddressFormat no longer has from_account_id() or to_account_id() methods. Use EthAccountIdFormat for AccountId ↔ Ethereum address conversions.
• The From<AccountId> for EthAddressFormat impl has been removed. Use EthAccountIdFormat::from(account_id) instead.

File Structure

The old address.rs has been split into:

• eth_address_format.rs — EthAddressFormat + AddressConversionError
• eth_account_id_format.rs — EthAccountIdFormat (imports from eth_address_format)

[bobbinth]

Question: why not do this as just EthAccountIdFormat(AccountId) - i.e., internal representation would be just AccountId, but we could convert to/from Ethereum address.

[mmagician]

I find the proposed naming distinction confusing: I often refer to Ethereum address as "account id" (maybe this is just me, it's probably not technically precise language), "account hex" or similar.

If we proceed with this refactoring then I'd much rather have the distinction very clear, maybe something like EthEmbeddedAccountId, or just EmbeddedAccountId (in eth_types module, so the import is clear eth_types::EmbeddedAccountId).