Remove site settings renderer, move it to flattened site settings loader - the...

Remove site settings renderer, move it to flattened site settings loader - the only place it is needed

Closes #3399190

config/install/core.entity_view_mode.site_setting_entity.teaser.yml

+langcode: en
+status: true
+dependencies:
+  module:
+    - site_settings
+  enforced:
+    module:
+      - site_settings
+id: site_setting_entity.teaser
+label: 'Teaser'
+targetEntityType: site_setting_entity
+cache: true