[IMP] web: improve time taken to parse owl templates

This commit removes some code that would allow one to define multiple
templates with the same name, and would cause the the last template with
a given name to override the previous one. This doesn't happen in
practice, nor should it, and the code that is used to allow it
repeatedly queries the document for a selector that is difficult to
process (selecting for elements with a specific attribute value,
especially when many elements in the document have that attribute).

A simple profile, with the crm and project apps installed, brings the
time that it takes to load the owl templates from ~200ms to ~35ms

closes odoo/odoo#132044

Signed-off-by: Francois Georis (fge) <fge@odoo.com>

addons/web/static/src/core/assets.js

@@ -113,21 +113,9 @@ export const _loadXML = (assets.loadXML = function loadXML(xml, app = defaultApp
     }
 
     for (const element of doc.querySelectorAll("templates > [t-name]")) {
-        const name = element.getAttribute("t-name");
-        const previous = templates.querySelector(`[t-name="${name}"]`);
-        if (previous) {
-            console.debug("Override template: " + name);
-            previous.replaceWith(element);
-        } else {
-            templates.documentElement.appendChild(element);
-        }
-    }
-    if (app || defaultApp) {
-        console.debug("Add templates in Owl app.");
-        app.addTemplates(templates, app || defaultApp);
-    } else {
-        console.debug("Add templates on window Owl container.");
+        templates.documentElement.appendChild(element);
     }
+    app?.addTemplates(templates, app);
 });
 /**
  * Update the default app to load templates.