change generated playbooks_keywords.rst to use an rst 'glossary' (#28843)

* Use a rst glossary for playbooks_keywords docs
* Add a 'Task' and 'Tasks' to glossary.
* Update keywords desciptions,
* use :term: rst ref, some quoting
* Make it more obvious that 'retries' and 'until' need to be used in combination.

docs/templates/playbooks_keywords.rst.j2

@@ -15,8 +15,12 @@ Be aware that this reflects the 'current development branch' and that the keywor
 
 {{ name }}
 {{ '-' * name|length }}
+.. glossary::
+
 {% for attribute in oblist[name]|sort %}
-  - **{{ attribute }}:** {{ oblist[name][attribute] }}
+    {{ attribute }}
+        {{ oblist[name][attribute] }}
+
 {% endfor %}
 
 {% endfor %}