[FIX] web: make pie chart title translatable

The Pie Chart title is not translatable, since a string defined in a
`t-att-` cannot be translated.

We use the attribute `title` instead.

Tests are adapted in https://github.com/odoo/enterprise/pull/3379

opw-1908220

closes odoo/odoo#29991

addons/web/static/src/js/widgets/pie_chart.js

@@ -31,6 +31,7 @@ var PieChart = Widget.extend({
             Domain.prototype.stringToArray(modifiers.domain || '[]'));
         var arch = qweb.render('web.PieChart', {
             modifiers: modifiers,
+            title: node.attrs.title || modifiers.title || modifiers.measure,
         });
 
         this.subViewParams = {

addons/web/static/src/xml/pie_chart.xml

@@ -1,7 +1,7 @@
 <template>
 
 <t t-name="web.PieChart">
-    <graph type="pie" t-att-title="modifiers.title || modifiers.measure">
+    <graph type="pie" t-att-title="title">
         <field t-att-name="modifiers.groupby.split(':')[0]" t-att-interval="modifiers.groupby.split(':')[1]"/>
         <field t-if="modifiers.measure" t-att-name="modifiers.measure" type="measure"/>
     </graph>