[IMP] core: _validate_fa_class_accessibility cleanups

* add t-out to set of text-generation attributes
* fix comment location
* don't handroll `iterancestors()`
* only check the `@string` on the toplevel button, doesn't really make
  sense that a button would contain a button in the first place (in
  fact it's not allowed per the HTML spec, a button can only contain
  *non-interactive phrasing content* cf 4.10.6)

Part-of: odoo/odoo#76581

odoo/addons/base/models/ir_ui_view.py

@@ -1749,7 +1749,7 @@ actual arch.
         valid_aria_attrs = {
             *att_names('title'), *att_names('aria-label'), *att_names('aria-labelledby'),
         }
-        valid_t_attrs = {'t-value', 't-raw', 't-field', 't-esc'}
+        valid_t_attrs = {'t-value', 't-raw', 't-field', 't-esc', 't-out'}
 
         ## Following or preceding text
         if (node.tail or '').strip() or (node.getparent().text or '').strip():
@@ -1769,15 +1769,15 @@ actual arch.
         if has_text(node.getnext()) or has_text(node.getprevious()):
             return
 
-        ## Aria label can be on ancestors
         def has_title_or_aria_label(node):
             return any(node.get(attr) for attr in valid_aria_attrs)
 
-        parent = node.getparent()
-        while parent is not None:
-            if has_title_or_aria_label(parent):
-                return
-            parent = parent.getparent()
+        ## Aria label can be on ancestors
+        if any(map(has_title_or_aria_label, node.iterancestors())):
+            return
+
+        if node.get('string'):
+            return
 
         ## And we ignore all elements with describing in children
         def contains_description(node, depth=0):
@@ -1789,8 +1789,6 @@ actual arch.
                 return True
             if node.tag in ('label', 'field'):
                 return True
-            if node.tag == 'button' and node.get('string'):
-                return True
             if node.text:  # not sure, does it match *[text()]
                 return True
             return any(contains_description(child, depth+1) for child in node)
@@ -1798,7 +1796,7 @@ actual arch.
         if contains_description(node):
             return
 
-        msg = ('%s must have title in its tag, parents, descendants or have text')
+        msg = '%s must have title in its tag, parents, descendants or have text'
         self._log_view_warning(msg % description, node)
 
     def _get_domain_identifiers(self, node, domain, use, expr=None):