op-supervisor: encode full hashes

[protolambda]

Description

This changes the op-supervisor DB format to be more secure and more convenient:

• Truncated hashes have a lot at stake, truncating to 20 bytes is possible but not ideal. See EIP https://eips.ethereum.org/EIPS/eip-3607
• Hashes can now be retrieved from the DB. Along with block number, timestamp, and parent hash, this allows a full block reference or head-pointer to be constructed from the DB content.

Additionally, merge the types packages of the supervisor (after removing the truncated-hash, it was just a single struct definition in a separate package otherwise)

Tests

Same tests still apply.

[protolambda]

@axelKingsley sorry, I forgot the EIP link. It's https://eips.ethereum.org/EIPS/eip-3607