Drop support for ansible-core 2.15; update CI to move ansible-core 2.16 to EOL CI; remove compat code for ansible-core < 2.14 (#10160)

* Drop support for ansible-core 2.15. Move 2.16 to EOL CI.

* Remove compatibility code for older ansible-core versions.

* Remove commented out parts.

meta/runtime.yml

@@ -3,7 +3,7 @@
 # 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
 
-requires_ansible: '>=2.15.0'
+requires_ansible: '>=2.16.0'
 action_groups:
   consul:
     - consul_agent_check