[FIX] web, website: correct items order on website systray

Before that commit, after the OWL2 rebase, the website systray items
were shuffled following those steps:
- Install website_blog
- Go to the posts list
- Click on a post
-> Until now, the systray items are correctly sorted
- Go back to the posts list, clicking on the blog navbar menu
-> Items are shuffled

For now, a temporary fix is to add an empty div with the index of the
item as the data-attribute to somehow force the rerender of the systray
items. That bug should be investigated further.

See merge commit for more information.

task-2687506

addons/web/static/src/webclient/navbar/navbar.xml

@@ -30,6 +30,8 @@
         <!-- Systray -->
         <div class="o_menu_systray d-flex flex-shrink-0 ml-auto" role="menu">
           <t t-foreach="systrayItems" t-as="item" t-key="item.key">
+            <!-- This ensures the correct order of the systray items -->
+            <div t-att-data-index="item.index"/>
             <ErrorHandler onError="error => this.handleItemError(error, item)">
                 <t t-component="item.Component" t-props="item.props"/>
             </ErrorHandler>

addons/website/static/src/components/navbar/navbar.js

@@ -59,7 +59,7 @@ patch(NavBar.prototype, 'website_navbar', {
         if (this.websiteService.currentWebsite) {
             return websiteSystrayRegistry
                 .getEntries()
-                .map(([key, value]) => ({ key, ...value }))
+                .map(([key, value], index) => ({ key, ...value, index }))
                 .filter((item) => ('isDisplayed' in item ? item.isDisplayed(this.env) : true))
                 .reverse();
         }