[PR #8477/ac3c0435 backport][stable-8] Update docsite chapter "Merging lists of dictionaries" (#8491)

Update docsite chapter "Merging lists of dictionaries" (#8477)

* Update docs 'Merging lists of dictionaries'

* Adding links to module and plugin options in
  docs/docsite/helper/lists_mergeby
* Add subsections and improve formatting.
* Add example-009 'Merge single list'

* Fix licenses.

* Fix variables.

* Update docs/docsite/helper/lists_mergeby/filter_guide_abstract_informations_merging_lists_of_dictionaries.rst.j2

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update docs/docsite/rst/filter_guide_abstract_informations_merging_lists_of_dictionaries.rst

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit ac3c04357c)

Co-authored-by: Vladimir Botka <vbotka@gmail.com>

docs/docsite/helper/lists_mergeby/default-common.yml

@@ -2,17 +2,11 @@
 # 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
-
 list1:
-  - name: foo
-    extra: true
-  - name: bar
-    extra: false
-  - name: meh
-    extra: true
+  - {name: foo, extra: true}
+  - {name: bar, extra: false}
+  - {name: meh, extra: true}
 
 list2:
-  - name: foo
-    path: /foo
-  - name: baz
-    path: /baz
+  - {name: foo, path: /foo}
+  - {name: baz, path: /baz}