[FIX] web_editor: conserve changes on edit link label

Issue:
======
When you update the link button label from the sidebar it loses its
style.

Steps to reproduce the issue:
=============================
- Got to website editor
- Insert a text block
- Added a button in the text block and any label
- Click on the button to edit it from the sidebar
- Change font size or font color or any style you want
- Update the label
- The style is lost

Origin of the issue:
====================
When updating the label, we search for the first child that has that
text, but when we have `ZWS start`  it will be considered as the first
child and then we update the inner text of the `a` element so we loose
the span of the text which has the custom styles.

Solution:
=========
We search for the first child which is not `ZWS`

task-3721686

closes odoo/odoo#157758

X-original-commit: 999d5787e3d8d0518692f987341dd6b298d7ffc4
Signed-off-by: Antoine Guenet (age) <age@odoo.com>

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

@@ -475,13 +475,17 @@ export class Link extends Component {
                 $link.html(this.state.originalHTML);
             } else if (linkInfos.content && linkInfos.content.length) {
                 let contentWrapperEl = $link[0];
-                // Update the first child element that has the same inner text
+                const text = $link[0].innerText.replaceAll("\u200B", "").trim();
+                // Update the first not ZWS child element that has the same inner text
                 // as the link with the new content while preserving child
                 // elements within the link. (e.g. the link is bold and italic)
-                while (contentWrapperEl.firstElementChild
-                    && (contentWrapperEl.firstElementChild.innerText === $link[0].innerText)) {
-                    contentWrapperEl = contentWrapperEl.firstElementChild;
-                }
+                let child;
+                do {
+                    contentWrapperEl = child || contentWrapperEl;
+                    child = [...contentWrapperEl.children].find(
+                        (element) => !element.hasAttribute("data-o-link-zws")
+                    );
+                } while (child?.innerText.replaceAll('\u200B', '').trim() === text);
                 contentWrapperEl.innerText = linkInfos.content;
             } else {
                 $link.text(linkInfos.url);