Deprecated host_key_checking option

* User can set host_key_checking configuration from
  connection plugins such as ssh and paramiko_ssh itself.
  Deprecate host_key_checking from global configuration.

Signed-off-by: Abhijeet Kasurde <Akasurde@redhat.com>

changelogs/fragments/deprecate_host_key_checking.yml

@@ -0,0 +1,3 @@
+---
+deprecated_features:
+  - config - deprecate host_key_checking from the global configuration.

lib/ansible/config/base.yml

@@ -1551,6 +1551,10 @@ HOST_KEY_CHECKING:
   ini:
   - {key: host_key_checking, section: defaults}
   type: boolean
+  deprecated:
+    why: This option was moved to the individual plugin itself
+    version: "2.22"
+    alternatives: Use the option from the plugin itself.
 HOST_PATTERN_MISMATCH:
   name: Control host pattern mismatch behaviour
   default: 'warning'