Unsafe initialization, message delivery, and nullifier patterns in aztec-nr

[AztecBot]

Context

Owner: @nventuro

Items

• TODO(F-239): assert_is_initialized_public is currently unsafe — nullifier existence doesn't prove public init complete (aztec-nr/aztec/src/macros/functions/initialization_utils.nr:29)
• TODO(14565): ONCHAIN_CONSTRAINED message delivery lacks constrained tag prefixing (aztec-nr/aztec/src/messages/message_delivery.nr:221)
• TODO(F-399): Orderbook pushes raw nullifier with no domain separator (noir-contracts/contracts/app/orderbook_contract/src/main.nr:149) — surrounding code by @benesjan