chore: replace u1 type with bool across noir-projects

[AztecBot]

Summary

Replaces all uses of the u1 type with bool across noir-projects, in preparation for noir-lang/noir#11753 which removes u1 from user-facing Noir.

Changes

Type replacements

• [u1; N] → [bool; N] (bit arrays from to_le_bits/to_be_bits)
• -> u1 → -> bool (function return types, especially AVM oracles)
• (x as u1) != 0 → x != 0 (field-to-boolean extraction)

Removed duplicate trait impls

Since bool already had FromField, ToField, Empty, Serialize, and Deserialize impls, the former u1 impls (now duplicates after renaming) were removed entirely:

• traits/from_field.nr — removed duplicate impl FromField for bool
• traits/to_field.nr — removed duplicate impl ToField for bool
• traits/empty.nr — removed duplicate impl Empty for bool
• serde/type_impls.nr — removed duplicate impl Serialize for bool and impl Deserialize for bool, plus unused U1_SERIALIZED_LEN constant

Files changed (17)

• aztec-nr/aztec/src/oracle/avm.nr — oracle return types
• aztec-nr/aztec/src/state_vars/mod.nr — doc comments
• noir-contracts/.../card_game_contract/src/game.nr — field extraction
• noir-contracts/.../orderbook_contract/src/order.nr — field extraction
• noir-contracts/.../aztec_sublib/src/oracle/avm.nr — oracle return types
• noir-contracts/.../avm_test_contract/src/main.nr — bit array types
• noir-protocol-circuits/crates/blob/... — bit arrays
• noir-protocol-circuits/crates/serde/... — removed u1 trait impls
• noir-protocol-circuits/crates/types/... — bit arrays, trait impls, field utils

ClaudeBox log: https://claudebox.work/s/d72e1449fb744a16?run=9