[FIX] web: hide handle on readonly x2m

The widget handle was displayed on x2m fields in form views, even when
the field was readonly, which makes no sense.

It is now correctly hidden.

Fixes #30580
opw-1937833

closes odoo/odoo#31743

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

addons/web/static/src/less/form_view.less

@@ -591,6 +591,9 @@
     &.o_form_readonly .o_field_widget .o_list_view .o_row_handle {
         display: none;  // Hide the handler in non-edit mode
     }
+    .o_field_widget.o_readonly_modifier .o_list_view .o_row_handle {
+        display: none;  // Hide the handler on readonly fields
+    }
 
     // Attachments
     .oe_attachment {

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

@@ -3487,6 +3487,43 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('embedded readonly one2many with handle widget', function (assert) {
+        assert.expect(4);
+
+        this.data.partner.records[0].turtles = [1, 2, 3];
+
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch:'<form string="Partners">' +
+                    '<sheet>' +
+                        '<field name="turtles" readonly="1">' +
+                            '<tree editable="top">' +
+                                '<field name="turtle_int" widget="handle"/>' +
+                                '<field name="turtle_foo"/>' +
+                            '</tree>' +
+                        '</field>' +
+                    '</sheet>' +
+                 '</form>',
+            res_id: 1,
+        });
+
+        assert.strictEqual(form.$('.o_row_handle').length, 3,
+            "there should be 3 handles (one for each row)");
+        assert.strictEqual(form.$('.o_row_handle:visible').length, 0,
+            "the handles should be hidden in readonly mode");
+
+        form.$buttons.find('.o_form_button_edit').click();
+
+        assert.strictEqual(form.$('.o_row_handle').length, 3,
+            "the handles should still be there");
+        assert.strictEqual(form.$('.o_row_handle:visible').length, 0,
+            "the handles should still be hidden (on readonly fields)");
+
+        form.destroy();
+    });
+
     QUnit.test('onchange for embedded one2many in a one2many with a second page', function (assert) {
         assert.expect(1);