feat: Use tail public inputs as transaction hash (#11100)

Implements AztecProtocol/aztec-packages#9269
Separates the role of the first nullifier and the transaction hash. The
transaction hash is now the hash of the tail public inputs. The first
nullifier is still used for note uniqueness and replayability protection

cpp/src/barretenberg/vm/avm/trace/trace.cpp

@@ -288,7 +288,8 @@ void AvmTraceBuilder::insert_private_revertible_state(const std::vector<FF>& sil
 
     for (size_t i = 0; i < siloed_note_hashes.size(); i++) {
         size_t note_index_in_tx = i + get_inserted_note_hashes_count();
-        FF nonce = AvmMerkleTreeTraceBuilder::unconstrained_compute_note_hash_nonce(get_tx_hash(), note_index_in_tx);
+        FF nonce =
+            AvmMerkleTreeTraceBuilder::unconstrained_compute_note_hash_nonce(get_first_nullifier(), note_index_in_tx);
         unique_note_hashes.push_back(
             AvmMerkleTreeTraceBuilder::unconstrained_compute_unique_note_hash(nonce, siloed_note_hashes.at(i)));
     }
@@ -3101,8 +3102,8 @@ AvmError AvmTraceBuilder::op_emit_note_hash(uint8_t indirect, uint32_t note_hash
     AppendTreeHint note_hash_write_hint = execution_hints.note_hash_write_hints.at(note_hash_write_counter++);
     FF siloed_note_hash = AvmMerkleTreeTraceBuilder::unconstrained_silo_note_hash(
         current_public_call_request.contract_address, row.main_ia);
-    FF nonce =
-        AvmMerkleTreeTraceBuilder::unconstrained_compute_note_hash_nonce(get_tx_hash(), inserted_note_hashes_count);
+    FF nonce = AvmMerkleTreeTraceBuilder::unconstrained_compute_note_hash_nonce(get_first_nullifier(),
+                                                                                inserted_note_hashes_count);
     FF unique_note_hash = AvmMerkleTreeTraceBuilder::unconstrained_compute_unique_note_hash(nonce, siloed_note_hash);
 
     ASSERT(unique_note_hash == note_hash_write_hint.leaf_value);

cpp/src/barretenberg/vm/avm/trace/trace.hpp

@@ -395,7 +395,7 @@ class AvmTraceBuilder {
     uint32_t get_inserted_note_hashes_count();
     uint32_t get_inserted_nullifiers_count();
     uint32_t get_public_data_writes_count();
-    FF get_tx_hash() const { return public_inputs.previous_non_revertible_accumulated_data.nullifiers[0]; }
+    FF get_first_nullifier() const { return public_inputs.previous_non_revertible_accumulated_data.nullifiers[0]; }
 
     // TODO: remove these once everything is constrained.
     AvmMemoryTag unconstrained_get_memory_tag(AddressWithMode addr);