Add conversion function for EVM address type (20 bytes) to `AccountId`

[partylikeits1983]

An Ethereum address is 20 bytes (160 bits).

The Miden AccountId is represented by two field elements: prefix & suffix:

prefix: [hash (56 bits) | storage mode (2 bits) | type (2 bits) | version (4 bits)]
suffix: [zero bit | hash (55 bits) | 8 zero bits]

So while technically the AccountId can be represented by 120 bits (the last 8 bits of the suffix are set to 0), for the purpose of this document it's easier to think of a 128-bit representation.

A Miden AccountId can be naturally embedded into an Ethereum address by setting the top 32 bits (4 bytes) to zero:
0x00000000 || prefix(8) || suffix(8).

A concrete example:

Representation	Value	Notes
Ethereum address	0x00000000b0E79c68cafC54802726C6F102Cca300	Last two hex nibbles are 00
Miden address (hex)	0xb0E79c68cafC54802726C6F102Cca3	Trailing 00 nibbles truncated by AccountId::to_hex()

Conversion to AccountId

EthAddressFormat::to_account_id() succeeds only when bytes[0..4] are all zero (the "Miden-embedded"
prefix). The remaining 16 bytes encode the AccountId:

prefix = bytes[4..12]  (big-endian u64)
suffix = bytes[12..20] (big-endian u64)
AccountId::try_from([prefix_felt, suffix_felt])

The reverse conversion (from_account_id) embeds the AccountId's prefix and suffix as
BE-bytes 4–11 and 12-19, respectively, with bytes 0–3 set to zero.

Required Functions

For the agglayer contracts we need Rust implementations of:

1. AccountId → EVM address (bytes20): EthAddressFormat::from_account_id(account_id: AccountId)
2. EVM address → AccountId: EthAddressFormat::to_account_id() -> AccountId
3. EVM address → Vec: EthAddressFormat::to_elements() -> Vec<Felt> Convert EVM address to field elements (used in constructing NoteStorage)

[partylikeits1983]

Closed by #2238