DEV: Rename experimental_passkeys to enable_passkeys (#24349)

Also includes a migration.

db/migrate/20231111201253_rename_experimental_passkeys_site_setting.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class RenameExperimentalPasskeysSiteSetting < ActiveRecord::Migration[7.0]
+  def up
+    execute "UPDATE site_settings SET name = 'enable_passkeys' WHERE name = 'experimental_passkeys'"
+  end
+
+  def down
+    execute "UPDATE site_settings SET name = 'experimental_passkeys' WHERE name = 'enable_passkeys'"
+  end
+end