feat!: init storage macro (#4200)

Closes: AztecProtocol/aztec-packages#3198,
AztecProtocol/aztec-packages#2928

~~Requires AztecProtocol/aztec-packages#4135,
which is blocked by noir-lang/noir#4124

Automatic storage initialization via aztec macro. 

Full support of public and private state from
`dep::aztec::state_vars::*`, including Maps (and nested Maps!)
Limited support for custom types (as long as they have a single
serializable generic and their constructor is `::new(context,
storage_slot`).

~~Pending: better errors, code comments and some cleanup.~~

Hijacking my own
[comment](AztecProtocol/aztec-packages#4200 (comment))
for the explanation:

The idea behind this is that in 99% of cases, storage initialization
(that is, the `impl` for a given `struct Storage...` is redundant, and
the only need for its existence was assigning storage slots...which in
turn were necessary because we didn't know how to serialize the data
structures that were used in a given contract or how much space they
used once serialized (relevant for the public state).

After AztecProtocol/aztec-packages#4135 is
merged, both of those things don't have to be explicitly provided since
we're using traits, so the aztec macro can infer the implementation of
the Storage struct just by taking hints from the definition. An example:

```rust
    struct Storage {
        // MyAwesomeStuff implements Serialize<2>, so we assign it slot 1 (and remember that it will take 2 slots due to its size)
        public_var: PublicState<MyAwesomeSuff>, 
        // Right after the first one, assign it to slot: current_slot + previous_size = 3
        another_public_var: PublicState<MyAwesomeSuff>,
        // Private and Public state don't share slots since they "live" in different trees, but keeping the slot count simplifies implementation. 
        // Notes also implement Serialize<N>, but they only take up 1 slot anyways because of hashing, assign it slot 5
        a_singleton: Singleton<ANote>,
        // Maps derive slots via hashing, so we can assume they only "take" 1 slot. We assign it slot 6
        balances: Map<AztecAddress, Singleton<ANote>>,
        // Slot 7
        a_set: Set<ANote>,
        // Slot 8
        imm_singleton: ImmutableSingleton<ANote>,
        // Slot 9. 
        profiles: Map<AztecAddress, Map<Singleton<ANote>>>,
    }

```

We have all the info we need in the AST and HIR to build this
automatically:

```rust
impl Storage {
    fn init(context: Context) -> Self {
        Storage {
            public_var: PublicState::new(context, 1), // No need for serialization methods, taken from the the trait impl
            another_public_var: PublicState::new(context, 3),
            a_singleton: Singleton::new(context, 5),
            // Map init lambda always takes the same form for known storage structs
            balances: Map::new(context, 6, |context, slot| { 
                Singleton::new(context, slot) 
            }),
            a_set: Set::new(context, 7),
            imm_singleton: ImmutableSingleton::new(context, 8),
            // A map of maps is just nesting lambdas, we can infer this too
            profiles: Map::new(context, 9, |context, slot| { 
                Map::new(context, slot, |context, slot| { 
                    Singleton::new(context, slot) 
                })
            })
        }
    }
}

```

...as long as we use "canonical" storage implementations. This means
`AStoragePrimitive<SomethingSerializable>` and
`Map<SomethingWithToField, AStoragePrimitive<SomethingSerializable>>`.

**TLDR:** define the Storage struct, in 99% of cases the macro takes
care of the implementation!

Implementing custom storage will look just like it does know, the macro
will skip automatic generation if it finds one.

---------

Co-authored-by: sirasistant <sirasistant@gmail.com>

aztec/src/state_vars.nr

@@ -4,3 +4,4 @@ mod public_state;
 mod set;
 mod singleton;
 mod stable_public_state;
+mod storage;

aztec/src/state_vars/immutable_singleton.nr

@@ -16,6 +16,7 @@ use crate::note::{
     note_viewer_options::NoteViewerOptions,
 };
 use crate::oracle::notes::check_nullifier_exists;
+use crate::state_vars::storage::Storage;
 
 // docs:start:struct
 struct ImmutableSingleton<Note> {
@@ -24,6 +25,8 @@ struct ImmutableSingleton<Note> {
 }
 // docs:end:struct
 
+impl<T> Storage<T> for ImmutableSingleton<T> {}
+
 impl<Note> ImmutableSingleton<Note> {
     // docs:start:new
     pub fn new(

aztec/src/state_vars/map.nr

@@ -4,6 +4,7 @@ use dep::protocol_types::{
     hash::pedersen_hash,
     traits::{ToField}
 };
+use crate::state_vars::storage::Storage;
 
 // docs:start:map
 struct Map<K, V> {
@@ -13,6 +14,8 @@ struct Map<K, V> {
 }
 // docs:end:map
 
+impl<K, T> Storage<T> for Map<K, T> {}
+
 impl<K, V> Map<K, V> {
     // docs:start:new
     pub fn new(

aztec/src/state_vars/public_state.nr

@@ -3,6 +3,7 @@ use crate::oracle::storage::storage_read;
 use crate::oracle::storage::storage_write;
 use dep::std::option::Option;
 use dep::protocol_types::traits::{Deserialize, Serialize};
+use crate::state_vars::storage::Storage;
 
 // docs:start:public_state_struct
 struct PublicState<T> {
@@ -11,6 +12,8 @@ struct PublicState<T> {
 }
 // docs:end:public_state_struct
 
+impl<T> Storage<T> for PublicState<T> {}
+
 impl<T> PublicState<T> {
     // docs:start:public_state_struct_new
     pub fn new(

aztec/src/state_vars/set.nr

@@ -15,6 +15,7 @@ use crate::note::{
     note_viewer_options::NoteViewerOptions,
     utils::compute_note_hash_for_consumption,
 };
+use crate::state_vars::storage::Storage;
 
 // docs:start:struct
 struct Set<Note> {
@@ -23,6 +24,8 @@ struct Set<Note> {
 }
 // docs:end:struct
 
+impl<T> Storage<T> for Set<T> {}
+
 impl<Note> Set<Note> {
     // docs:start:new
     pub fn new(
@@ -36,7 +39,6 @@ impl<Note> Set<Note> {
         }
     }
     // docs:end:new
-
     // docs:start:insert
     pub fn insert<N>(self,
         note: &mut Note,

aztec/src/state_vars/singleton.nr

@@ -20,6 +20,7 @@ use crate::oracle::{
     nullifier_key::get_nullifier_secret_key,
     notes::check_nullifier_exists,
 };
+use crate::state_vars::storage::Storage;
 
 // docs:start:struct
 struct Singleton<Note> {
@@ -28,6 +29,8 @@ struct Singleton<Note> {
 }
 // docs:end:struct
 
+impl<T> Storage<T> for Singleton<T> {}
+
 impl<Note> Singleton<Note> {
     // docs:start:new
     pub fn new(

aztec/src/state_vars/stable_public_state.nr

@@ -5,12 +5,15 @@ use crate::oracle::{
 use crate::history::public_value_inclusion::prove_public_value_inclusion;
 use dep::std::option::Option;
 use dep::protocol_types::traits::{Deserialize, Serialize};
+use crate::state_vars::storage::Storage;
 
 struct StablePublicState<T>{
     context: Context,
     storage_slot: Field,
 }
 
+impl<T> Storage<T> for StablePublicState<T> {}
+
 impl<T> StablePublicState<T> {
     pub fn new(
         // Note: Passing the contexts to new(...) just to have an interface compatible with a Map.

aztec/src/state_vars/storage.nr

@@ -0,0 +1,8 @@
+use crate::context::{Context};
+use dep::protocol_types::traits::{Deserialize, Serialize};
+
+trait Storage<T> where T: Serialize<N> + Deserialize<N> {
+    fn get_storage_slot(self) -> Field {
+        self.storage_slot
+    }
+}