Vault secrets default vault ids list (#28190)

* Add config option for a default list of vault-ids

This is the vault-id equilivent of ANSIBLE_DEFAULT_PASSWORD_FILE
except ANSIBLE_DEFAULT_VAULT_IDENTITY_LIST is a list.

lib/ansible/cli/__init__.py

@@ -214,6 +214,9 @@ class CLI(with_metaclass(ABCMeta, object)):
         # certain vault password prompt format, so 'promp_ask_vault_pass' vault_id gets the old format.
         prompt_formats = {}
 
+        # If there are configured default vault identities, they are considered 'first'
+        # so we prepend them to vault_ids (from cli) here
+
         vault_password_files = vault_password_files or []
         if C.DEFAULT_VAULT_PASSWORD_FILE:
             vault_password_files.append(C.DEFAULT_VAULT_PASSWORD_FILE)