chore(avm-context): implement Empty (#6303)

Will be needed for https://github.com/AztecProtocol/aztec-packages/blob/master/noir-projects/aztec-nr/aztec/src/state_vars/shared_mutable/shared_mutable.nr#L132 .

noir-projects/aztec-nr/aztec/src/context/avm_context.nr

@@ -3,7 +3,7 @@ use dep::protocol_types::{
     address::{AztecAddress, EthAddress},
     constants::{L1_TO_L2_MESSAGE_LENGTH, NESTED_CALL_L2_GAS_BUFFER}, header::Header
 };
-use dep::protocol_types::traits::Serialize;
+use dep::protocol_types::traits::{Deserialize, Serialize, Empty};
 use dep::protocol_types::abis::function_selector::FunctionSelector;
 use dep::protocol_types::abis::public_circuit_public_inputs::PublicCircuitPublicInputs;
 use crate::context::inputs::avm_context_inputs::AvmContextInputs;
@@ -191,6 +191,12 @@ impl ContextInterface for AvmContext {
     }
 }
 
+impl Empty for AvmContext {
+    fn empty() -> Self {
+        AvmContext::new(AvmContextInputs::empty())
+    }
+}
+
 // Helper functions
 fn gas_for_call(user_gas: GasOpts) -> [Field; 2] {
     [

noir-projects/aztec-nr/aztec/src/context/inputs/avm_context_inputs.nr

@@ -1,4 +1,15 @@
+use dep::protocol_types::traits::Empty;
+
 struct AvmContextInputs {
     selector: Field,
     args_hash: Field,
 }
+
+impl Empty for AvmContextInputs {
+    fn empty() -> Self {
+        AvmContextInputs {
+            selector: 0,
+            args_hash: 0,
+        }
+    }
+}