feat: removing redundant key fetching (#8043)

Fixes #7954

I replaced the use of `encode_and_encrypt_note` with
`encode_and_encrypt_note_with_keys` in most of the places as it allowed
for reusing the obtained keys. Note that there is only 1 legimate place
remaining where it made sense to keep on using `encode_and_encrypt_note`
and that is
[here](https://github.com/AztecProtocol/aztec-packages/blob/34ae51df5d45973deb3408075a50070c781f7a48/noir-projects/noir-contracts/contracts/app_subscription_contract/src/main.nr#L47).
All the other places are either test contracts or the token blacklist
contract which is very outdated by now and hence it didn't seem to be
worth it to update it.

Given this I think we should nuke `encode_and_encrypt_note` to keep the
API simpler and to make devs write efficient code. Does the reviewer
agree? (possibly also `encode_and_encrypt_event`)

Token::transfer(...) gates before were 49296 and after 38903. Diff of
**10393 gates**.

easy-private-state/src/easy_private_uint.nr

@@ -1,7 +1,7 @@
 use dep::aztec::{
     context::PrivateContext, protocol_types::{address::AztecAddress},
     note::note_getter_options::NoteGetterOptions, state_vars::PrivateSet,
-    encrypted_logs::encrypted_note_emission::encode_and_encrypt_note,
+    encrypted_logs::encrypted_note_emission::encode_and_encrypt_note_with_keys,
     keys::getters::get_current_public_keys
 };
 use dep::value_note::{filter::filter_notes_min_sum, value_note::ValueNote};
@@ -24,19 +24,28 @@ impl<Context> EasyPrivateUint<Context> {
 impl<Context> EasyPrivateUint<&mut PrivateContext> {
     // Very similar to `value_note::utils::increment`.
     pub fn add(self, addend: u64, owner: AztecAddress, outgoing_viewer: AztecAddress) {
-        let owner_npk_m_hash = get_current_public_keys(self.context, owner).npk_m.hash();
+        let owner_keys = get_current_public_keys(self.context, owner);
+        let outgoing_viewer_keys = get_current_public_keys(self.context, outgoing_viewer);
         // Creates new note for the owner.
-        let mut addend_note = ValueNote::new(addend as Field, owner_npk_m_hash);
+        let mut addend_note = ValueNote::new(addend as Field, owner_keys.npk_m.hash());
 
         // Insert the new note to the owner's set of notes.
         // docs:start:insert
-        self.set.insert(&mut addend_note).emit(encode_and_encrypt_note(self.context, outgoing_viewer, owner));
+        self.set.insert(&mut addend_note).emit(
+            encode_and_encrypt_note_with_keys(
+                self.context,
+                outgoing_viewer_keys.ovpk_m,
+                owner_keys.ivpk_m,
+                owner
+            )
+        );
         // docs:end:insert
     }
 
     // Very similar to `value_note::utils::decrement`.
     pub fn sub(self, subtrahend: u64, owner: AztecAddress, outgoing_viewer: AztecAddress) {
-        let owner_npk_m_hash = get_current_public_keys(self.context, owner).npk_m.hash();
+        let owner_keys = get_current_public_keys(self.context, owner);
+        let outgoing_viewer_keys = get_current_public_keys(self.context, outgoing_viewer);
 
         // docs:start:pop_notes
         let options = NoteGetterOptions::with_filter(filter_notes_min_sum, subtrahend as Field);
@@ -56,7 +65,14 @@ impl<Context> EasyPrivateUint<&mut PrivateContext> {
 
         // Creates change note for the owner.
         let result_value = minuend - subtrahend;
-        let mut result_note = ValueNote::new(result_value as Field, owner_npk_m_hash);
-        self.set.insert(&mut result_note).emit(encode_and_encrypt_note(self.context, outgoing_viewer, owner));
+        let mut result_note = ValueNote::new(result_value as Field, owner_keys.npk_m.hash());
+        self.set.insert(&mut result_note).emit(
+            encode_and_encrypt_note_with_keys(
+                self.context,
+                outgoing_viewer_keys.ovpk_m,
+                owner_keys.ivpk_m,
+                owner
+            )
+        );
     }
 }

value-note/src/utils.nr

@@ -1,6 +1,6 @@
 use dep::aztec::prelude::{AztecAddress, PrivateContext, PrivateSet, NoteGetterOptions};
 use dep::aztec::note::note_getter_options::SortOrder;
-use dep::aztec::encrypted_logs::encrypted_note_emission::encode_and_encrypt_note;
+use dep::aztec::encrypted_logs::encrypted_note_emission::encode_and_encrypt_note_with_keys;
 use dep::aztec::keys::getters::get_current_public_keys;
 use crate::{filter::filter_notes_min_sum, value_note::{ValueNote, VALUE_NOTE_LEN, VALUE_NOTE_BYTES_LEN}};
 
@@ -19,11 +19,19 @@ pub fn increment(
     recipient: AztecAddress,
     outgoing_viewer: AztecAddress // docs:end:increment_args
 ) {
-    let recipient_npk_m_hash = get_current_public_keys(balance.context, recipient).npk_m.hash();
+    let recipient_keys = get_current_public_keys(balance.context, recipient);
+    let outgoing_viewer_ovpk_m = get_current_public_keys(balance.context, outgoing_viewer).ovpk_m;
 
-    let mut note = ValueNote::new(amount, recipient_npk_m_hash);
+    let mut note = ValueNote::new(amount, recipient_keys.npk_m.hash());
     // Insert the new note to the owner's set of notes and emit the log if value is non-zero.
-    balance.insert(&mut note).emit(encode_and_encrypt_note(balance.context, outgoing_viewer, recipient));
+    balance.insert(&mut note).emit(
+        encode_and_encrypt_note_with_keys(
+            balance.context,
+            outgoing_viewer_ovpk_m,
+            recipient_keys.ivpk_m,
+            recipient
+        )
+    );
 }
 
 // Find some of the `owner`'s notes whose values add up to the `amount`.