DEV: Implement glimmer topic-list (#26743)

(experimental)

The initial implementation of glimmer topic-list and related components. Does not include new APIs and isn't compatible with existing customization. That's gonna come in future PRs.

Enabled by adding groups to `experimental_glimmer_topic_list_groups` setting.

config/locales/server.en.yml

@@ -2647,6 +2647,7 @@ en:
     enable_experimental_lightbox: "EXPERIMENTAL: Replace the default image lightbox with the revamped design."
     enable_experimental_bookmark_redesign_groups: "EXPERIMENTAL: Show a quick access menu for bookmarks on posts and a new redesigned modal"
     glimmer_header_mode: "Control whether the new 'glimmer' header implementation is used. Defaults to 'auto', which will enable automatically once all your themes and plugins are ready. https://meta.discourse.org/t/296544"
+    experimental_glimmer_topic_list_groups: "EXPERIMENTAL: Enable the new 'glimmer' topic list implementation. This implementation is under active development, and is not intended for production use. Do not develop themes/plugins against it until the implementation is finalized and announced."
     experimental_form_templates: "EXPERIMENTAL: Enable the form templates feature. <b>After enabled,</b> manage the templates at <a href='%{base_path}/admin/customize/form-templates'>Customize / Templates</a>."
     admin_sidebar_enabled_groups: "EXPERIMENTAL: Enable sidebar navigation for the admin UI for the specified groups, which replaces the top-level admin navigation buttons."
     lazy_load_categories_groups: "EXPERIMENTAL: Lazy load category information only for users of these groups. This improves performance on sites with many categories."

config/site_settings.yml

@@ -2352,6 +2352,13 @@ developer:
     default: ""
     allow_any: false
     refresh: true
+  experimental_glimmer_topic_list_groups:
+    client: true
+    type: group_list
+    list_type: compact
+    default: ""
+    allow_any: false
+    refresh: true
   enable_experimental_lightbox:
     default: false
     client: true