[FIX] web: re-add title attribute for many2many tags that got lost

Co-authored-by: Nicolas Martinelli <nim@odoo.com>

Closes #25693

addons/web/static/src/xml/base.xml

@@ -834,7 +834,7 @@
     <t t-foreach="elements" t-as="el">
         <t t-set="color" t-value="el[colorField] || 0"/>
         <span t-attf-class="badge dropdown o_tag_color_#{color}" t-att-data-color="color" t-att-data-index="el_index" t-att-data-id="el.id">
-            <span class="o_badge_text"><t t-esc="el.display_name"/></span>
+            <span class="o_badge_text" t-att-title="el.display_name"><t t-esc="el.display_name"/></span>
             <span t-if="!readonly" class="fa fa-times o_delete"/>
         </span>
     </t>

addons/web/static/tests/fields/relational_fields_tests.js

@@ -10483,6 +10483,31 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('widget many2many_tags', function (assert) {
+        assert.expect(1);
+        this.data.turtle.records[0].partner_ids = [2];
+
+        var form = createView({
+            View: FormView,
+            model: 'turtle',
+            data: this.data,
+            arch:'<form string="Turtles">' +
+                    '<sheet>' +
+                        '<field name="display_name"/>' +
+                        '<field name="partner_ids" widget="many2many_tags"/>' +
+                    '</sheet>' +
+                '</form>',
+            res_id: 1,
+        });
+
+        assert.deepEqual(
+            form.$('.o_field_many2manytags.o_field_widget .badge .o_badge_text').attr('title'),
+            'second record', 'the title should be filled in'
+        );
+
+        form.destroy();
+    });
+
     QUnit.module('FieldStatus');
 
     QUnit.test('static statusbar widget on many2one field', function (assert) {