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

spec/system/composer/default_to_subcategory_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 describe "Default to Subcategory when parent Category doesn't allow posting", type: :system do
-  fab!(:user)
+  fab!(:user) { Fabricate(:user, refresh_auto_groups: true) }
   fab!(:group)
   fab!(:group_user) { Fabricate(:group_user, user: user, group: group) }
   fab!(:default_latest_category) { Fabricate(:category, name: "General") }