Views FilterPluginBase::groupForm double translates group item label strings

Problem/Motivation

FilterPluginBase::groupForm potentially passes already translated values (via configuration translation through t() which can unnecessarily translate said values and insert unneeded strings into locale storage. The code segment below in /core/modules/views/src/Plugin/views/filter/FilterPluginBase.php is causing this issue.

    foreach ($this->options['group_info']['group_items'] as $id => $group) {
      if (!empty($group['title'])) {
        $groups[$id] = $id != 'All' ? $this->t($group['title']) : $group['title'];
      }
    }

Steps to reproduce

1. Create a view on a multilingual site that has at least one other language enabled
2. Configuration translation and user interface translation should be enabled
3. Set up a new view and a page display, add an exposed filter for a field that uses "Grouped filters", add some group items and add labels for them
4. Access the view page in the non-default language, this will register the group item labels for user interface translation
5. Translate the view + display via configuration translation and add unique language values for the group labels there
6. Access the view page in the non-default language again, views will show the group item labels via configuration translation AND register them as new user interface strings to be translated.

Proposed resolution

Rely on configuration translation instead of string translation through t(). We can remove the conditional logic and revise it to:

    foreach ($this->options['group_info']['group_items'] as $id => $group) {
      if (!empty($group['title'])) {
        $groups[$id] = $group['title'];
      }
    }