Decode vaulted args before sending over ansible-connection. (#78236)

I'm not aware of a way to easily get vault secrets decoded on the
ansible-connection side without sending the vault secrets over the
connection in the same way, so just decode them for transport.

changelogs/fragments/ansible-connection_decode.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - ansible-connection - decrypt vaulted parameters before sending over the socket, as
+    vault secrets are not available on the other side.

lib/ansible/module_utils/connection.py

@@ -144,7 +144,7 @@ class Connection(object):
             )
 
         try:
-            data = json.dumps(req, cls=AnsibleJSONEncoder)
+            data = json.dumps(req, cls=AnsibleJSONEncoder, vault_to_text=True)
         except TypeError as exc:
             raise ConnectionError(
                 "Failed to encode some variables as JSON for communication with ansible-connection. "