[FIX] website: restore hidden indicators in gallery snippet

Indicators were hidden in editor when switching to slideshow mode
from any other mode. Because the class of the selected mode was defined
after rendering and we need this class before the rendering. This also
fixes other small issues when switching between different modes.

Part of https://github.com/odoo/odoo/pull/44180
task-2162952

closes odoo/odoo#47519

X-original-commit: a99150b11a463901121bbe9751370231e3564ca2
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website/static/src/snippets/s_image_gallery/options.js

@@ -205,10 +205,10 @@ options.registry.gallery = options.Class.extend({
     mode: function (previewMode, widgetValue, params) {
         widgetValue = widgetValue || 'slideshow'; // FIXME should not be needed
         this.$target.css('height', '');
-        this[widgetValue]();
         this.$target
             .removeClass('o_nomode o_masonry o_grid o_slideshow')
             .addClass('o_' + widgetValue);
+        this[widgetValue]();
         this.trigger_up('cover_update');
     },
     /**