locale_gen: works with C.UTF-8 (#6774)

* locale_gen: fix

* test working with C.UTF-8

* working with locale eo

* handle C.UTF-8 edge cases

* grammatic pedantism

* add changelog frag

* add doc about specific OS support

* update changelog frag

tests/integration/targets/locale_gen/vars/main.yml

@@ -0,0 +1,17 @@
+---
+# Copyright (c) Ansible Project
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+# locale_basic: pt_BR
+
+locale_list_basic:
+  - localegen: pt_BR
+    locales: [pt_BR]
+    skip_removal: false
+  - localegen: C.UTF-8
+    locales: [C.utf8, C.UTF-8]
+    skip_removal: true
+  - localegen: eo
+    locales: [eo]
+    skip_removal: false