[FIX] mail: no write on read-only SuggestedRecipientInfo/isSelected

Before this commit, when a recipient is suggested in composer header
and current user click on checkbox, there was the following warning
in the console:

```
read-only SuggestedRecipientInfo/isSelected on record(SuggestedRecipientInfo_1) was updated
```

The state of a selected suggested recipient is determined by being
manually selected on UI, but also that there's a partner related
to this recipient. `isSelected` is a computed field with itself
as dependency, and it was also imperatively set. We don't want
any computed field to be set imperatively, hence the warning in
the console.

This commit fixes the issue by introducing another field that
is specific to selection on UI by current user. This field does
not depend on whether there's a partner. This field is imperatively
set, and then `isSelected` is fully declarative as a computed field
with no self dependency and no imperative update.

Task-3032869

closes odoo/odoo#103573

X-original-commit: 8e2980e1e871a8046f09d3d0affb6400ee030eeb
Signed-off-by: Louis Wicket (wil) <wil@odoo.com>
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/components/composer_suggested_recipient/composer_suggested_recipient.js

@@ -62,7 +62,7 @@ export class ComposerSuggestedRecipient extends Component {
             return;
         }
         const isChecked = this._checkboxRef.el.checked;
-        this.composerSuggestedRecipientView.suggestedRecipientInfo.update({ isSelected: isChecked });
+        this.composerSuggestedRecipientView.suggestedRecipientInfo.update({ isChecked });
         if (!this.composerSuggestedRecipientView.suggestedRecipientInfo.partner) {
             // Recipients must always be partners. On selecting a suggested
             // recipient that does not have a partner, the partner creation form

addons/mail/static/src/models/suggested_recipient_info.js

@@ -32,6 +32,12 @@ registerModel({
         id: attr({
             identifying: true,
         }),
+        /**
+         * Determines whether this suggested recipient has been checked on UI.
+         * A suggested recipient info is checked when current user manually set
+         * checkbox to "checked" value.
+         */
+        isChecked: attr(),
         /**
          * Determines whether `this` will be added to recipients when posting a
          * new message on `this.thread`.
@@ -41,7 +47,7 @@ registerModel({
              * Prevents selecting a recipient that does not have a partner.
              */
             compute() {
-                return this.partner ? this.isSelected : false;
+                return this.partner ? this.isChecked : false;
             },
             default: true,
         }),