[FIX] web_editor: do not create variant image while selecting an image

Steps to reproduce the bug:
- Go on a product page of a product with multiple variants but no image
set for those variants. Because there is no image set to those variants,
the variant images fall back on the template image.
- Edit.
- Click on the variant image of the product. (Note that `.o_dirty` is
added to the element).
- Save.

-> The image of the product is not the template image anymore but a
variant image that is the same as the template image.

Because `.o_dirty` is added while clicking on the product image,
`save_embedded_field()` will set the `image_1920` field of
`product.product`. Because the product has multiple variants, the
`image_variant_1920` field of `product.product` is modified see
(`_set_template_field()`).

The problem is that the `o_dirty` class is added on the clicked element.
To solve the problem, the `MutationObserver` responsible for adding this
class is paused when modifying the tooltips. Note that it was introduced
by [1] but it was broken since [2].

[1]: https://github.com/odoo/odoo/commit/9f93fa8e77b11da2fcf60f606784eec49a94778a
[2]: https://github.com/odoo/odoo/commit/8eb0ca54200f0f8e1078bb6a0d507e747ccea122

task-3111601

X-original-commit: 3b8f601f95845d65a515e9c8bb8e25cc17565dbf
Part-of: odoo/odoo#133546

addons/web_editor/static/src/js/wysiwyg/wysiwyg.js

@@ -2179,13 +2179,13 @@ export class Wysiwyg extends Component {
                 if (!this.showTooltip || $target.attr('title') !== undefined) {
                     return;
                 }
-                this.odooEditor.observerUnactive();
                 // Tooltips need to be cleared before leaving the editor.
                 this.saving_mutex.exec(() => {
+                    this.odooEditor.observerUnactive();
                     $target.tooltip({title: _t('Double-click to edit'), trigger: 'manual', container: 'body'}).tooltip('show');
+                    this.odooEditor.observerActive();
                     this.tooltipTimeouts.push(setTimeout(() => $target.tooltip('dispose'), 800));
                 });
-                this.odooEditor.observerActive();
             }, 400));
         }
         // Hide button groups that have no visible buttons.