[FIX] mail: improve performance of JS write, especially for x2m

- store `x2many` values as `Set`. This is conceptually more correct because
  duplicates were already not allowed, and using a `Set` allows for much faster
  operations such as checking the presence of a record in the relation, which is
  done at every write, for every linked record.

- `stringify` in `write` was slow and unnecessary because we can always assume
  that new non-primitive should be provided to `write`

- remove field values from store, in favor of just storing a counter, which is
  enough to trigger renders. This allows to get rid of one Proxy level around
  data, which was slower, but which also prevented from using `Set`.

- write in store exactly once per update cycle, to trigger one `useStore` call
  on each component. Records keep `__state` but as a local counter, to let
  `useStore` know which records have been updated (easier to compare a counter
  than comparing each and every field value).

Results
=======

The worse case test (using a lot of x2m) that was used to benchmark this PR
`form_renderer_tests.js` of `mail_enterprise` went from taking around 4s before
this commit, to around 2.5s after this commit.
And the worse `_setRelationLinkMany2Many` previously took around 250ms, and it
now takes around 50ms.

The whole `mail` QUnit suite took around 55s before, now around 42s.

Part of task-2308312

closes odoo/odoo#55248

X-original-commit: 4db0a10d85534ef896f6bcbf13bca4983a6e2003
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/addons/mail/static/src/model/model_manager.js b/addons/mail/static/src/model/model_manager.js
index 37ce2d2808c..5ef0d5c19ae 100644
--- a/addons/mail/static/src/model/model_manager.js
+++ b/addons/mail/static/src/model/model_manager.js
@@ -122,11 +122,10 @@ class ModelManager {
         const record = new Model({ valid: true });
         Object.defineProperty(record, 'env', { get: () => Model.env });
         record.localId = record._createRecordLocalId(data);
-
-        // Make state, which contain field values of record that have to
-        // be observed in store.
-        this.env.store.state[record.localId] = {};
-        record.__state = this.env.store.state[record.localId];
+        // Contains field values of record.
+        record.__values = {};
+        // Contains revNumber of record for checking record update in useStore.
+        record.__state = 0;
 
         // Make proxified record, so that access to field redirects
         // to field getter.
@@ -299,6 +298,8 @@ class ModelManager {
             }
             this._toComputeFields.clear();
             this._isInUpdateCycle = false;
+            // trigger at most one useStore call per update cycle
+            this.env.store.state.messagingRevNumber++;
         } else {
             this._updateDirect(record, data);
             if (this._isHandlingToUpdateAfters) {
@@ -689,8 +690,8 @@ class ModelManager {
             }
             if (field.fieldType === 'relation') {
                 if (['one2many', 'many2many'].includes(field.relationType)) {
-                    // Ensure X2many relations are arrays by defaults.
-                    field.write(record, [], { registerDependents: false });
+                    // Ensure X2many relations are Set by defaults.
+                    field.write(record, new Set(), { registerDependents: false });
                 } else {
                     field.write(record, undefined, { registerDependents: false });
                 }