[FIX] web: control panel date filter ok in arabic

The date filters sent to servers were being computed in current locale,
so in arabic we would get things like this:

- "٢٠١٩-١٢-٠٩" instead of "2019-12-09"
- "٢٠١٩-١٢-٠٩ ١٦:١٦:١٥" instead of "2019-12-09 16:16:15"

which would cause a traceback in backend.

opw-2122333
closes #41570

closes odoo/odoo#41596

X-original-commit: da778afc24b048244467649dfa4af4e6f4a78e44
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>

addons/web/static/src/js/views/control_panel/control_panel_view.js

@@ -231,8 +231,8 @@ var ControlPanelView = Factory.extend({
             const setParam = _.extend({}, y.setParam, o ? o.setParam : {});
             const granularity = o ? o.granularity : y.granularity;
             const date = this.referenceMoment.clone().set(setParam).add(addParam);
-            let leftBound = date.clone().startOf(granularity);
-            let rightBound = date.clone().endOf(granularity);
+            let leftBound = date.clone().startOf(granularity).locale('en');
+            let rightBound = date.clone().endOf(granularity).locale('en');
 
             if (filter.fieldType === 'date') {
                 leftBound = leftBound.format("YYYY-MM-DD");