[FIX] web, mass_mailing, website: remove frontend debug icon

After [1] moved the website edition in the backend, we feel that the
code required to make the additional debug icon in the footer of the
frontend still work is not worth it.

Before this commit, on a website page, it was not working: clicking on
it from the WebsitePreview client action would only remove the debug
mode of the frontend, and the backend would keep it.
The user can now leave the debug mode from the debug menu systray item
and we consider that leaving debug mode as a visitor (from the
frontend) is not a feature worth keeping.

[1]: https://github.com/odoo/odoo/commit/31cc10b91dc7762e23b4bde9b945be0c4ce3fe3b

task-2687506

closes odoo/odoo#95499

Related: odoo/upgrade#3721
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/mass_mailing/views/mailing_templates_portal_layouts.xml

@@ -26,7 +26,6 @@
                         <a target="_blank" class="label label-danger" href="https://www.odoo.com/app/website">Odoo</a>
                     </div>
                     <div class="float-start text-muted" itemscope="itemscope" itemtype="https://schema.org/Organization">
-                        <t t-call="web.debug_icon"/>
                         Copyright &amp;copy; <span t-field="res_company.name" itemprop="name">Company name</span>
                     </div>
                 </div>

addons/web/views/webclient_templates.xml

@@ -66,7 +66,6 @@
                         <div class="container py-3">
                             <div class="row">
                                 <div class="col-sm text-center text-sm-start text-muted">
-                                    <t t-call="web.debug_icon"/>
                                     <span class="o_footer_copyright_name me-2">Copyright &amp;copy; <span t-field="res_company.name" itemprop="name">Company name</span></span>
                                 </div>
                                 <div class="col-sm text-center text-sm-end">
@@ -319,12 +318,4 @@
         </t>
     </template>
 
-    <template id="debug_icon" name="Debug Icon">
-        <t t-if="debug" t-nocache="The query strings and debug mode can change for the same page and the same rendering.">
-            <t t-set="debug_mode_help" t-value="' (%s)' % debug if debug != '1' else ''"/>
-            <a t-attf-href="?#{keep_query('*', debug='')}" t-attf-title="Debug mode is activated#{debug_mode_help}. Click here to exit debug mode."
-               class="o_debug_mode"><span class="fa fa-bug"/></a>
-        </t>
-    </template>
-
 </odoo>

addons/website/tests/test_page.py

@@ -304,15 +304,6 @@ class WithContext(HttpCase):
         canonical_url = root_html.xpath('//link[@rel="canonical"]')[0].attrib['href']
         self.assertIn(canonical_url, [f"{website.domain}/", f"{website.domain}/page_1"])
 
-    def test_t_cache_footer_debug_link(self):
-        # Debug link (flag) should be use the current url.
-        self.url_open('/')
-        self.url_open('/contactus')
-        r = self.url_open('/?debug=1')
-        self.assertIn('<a class="o_debug_mode" href="?debug="', r.text)
-        r = self.url_open('/contactus?name=MyName')  # don't force debug here, already done on previous step
-        self.assertIn('<a class="o_debug_mode" href="?debug=&amp;name=MyName"', r.text)
-
     def test_07_alternatives(self):
         website = self.env.ref('website.default_website')
         lang_fr = self.env['res.lang']._activate_lang('fr_FR')