DEV: Convert min_trust_to_create_topic to groups (#24740)

This change converts the min_trust_to_create_topic site setting to
create_topic_allowed_groups.

See: https://meta.discourse.org/t/283408

- Hides the old setting
- Adds the new site setting
- Add a deprecation warning
- Updates to use the new setting
- Adds a migration to fill in the new setting if the old setting was
changed
- Adds an entry to the site_setting.keywords section
- Updates tests to account for the new change
- After a couple of months, we will remove the min_trust_to_create_topicsetting entirely.

Internal ref: /t/117248

lib/site_settings/deprecated_settings.rb

@@ -21,6 +21,7 @@ module SiteSettings::DeprecatedSettings
     ["email_in_min_trust", "email_in_allowed_groups", false, "3.3"],
     ["min_trust_to_edit_wiki_post", "edit_wiki_post_allowed_groups", false, "3.3"],
     ["allow_uploaded_avatars", "uploaded_avatars_allowed_groups", false, "3.3"],
+    ["min_trust_to_create_topic", "create_topic_allowed_groups", false, "3.3"],
   ]
 
   def setup_deprecated_methods