[IMP] web: add hover description for kanban progressbar sum field

This commit adds a sum field description when hovering the quantity at the end
of a progressbar. The description is the label (translated string
representation) of the field used for the sum.

Task-ID: 2243913
PR odoo/odoo#69380

addons/web/static/src/legacy/js/views/kanban/kanban_column_progressbar.js

@@ -35,6 +35,7 @@ var KanbanColumnProgressBar = Widget.extend({
             __false: 'muted', // color to use for false value
         });
         this.sumField = columnState.progressBarValues.sum_field;
+        this.sumFieldLabel = this.sumField ? columnState.fields[this.sumField].string : false;
 
         // Previous progressBar state
         var state = options.progressBarStates[this.columnID];

addons/web/static/src/legacy/xml/kanban.xml

@@ -117,7 +117,7 @@
                     t-attf-style="width: #{count ? (count * 100 / widget.groupCount) : 0}%;"/>
             </t>
         </div>
-        <div class="o_kanban_counter_side"><b><t t-esc="widget.totalCounterValue || 0"/></b></div>
+        <div class="o_kanban_counter_side" t-att-title="widget.sumFieldLabel || ''"><b><t t-esc="widget.totalCounterValue || 0"/></b></div>
     </div>
 </t>