fix decrypted vault utf8 values (#37539)

* Fix errors decrypted non-ascii vault vars

AnsibleVaultEncryptedUnicode was just using b"".decode()
instead of to_text() on the bytestrings returned from
vault.decrypt() and could cause errors on python2
if non-ascii since decode() defaults to ascii.
Use to_text() to default to decoding utf-8.

add intg and unit tests for value of vaulted vars
being non-ascii utf8

based on https://github.com/ansible/ansible/issues/37258

Fixes #37258

* yamllint fixups

lib/ansible/parsing/yaml/objects.py

@@ -104,7 +104,7 @@ class AnsibleVaultEncryptedUnicode(yaml.YAMLObject, AnsibleBaseYAMLObject):
         if not self.vault:
             # FIXME: raise exception?
             return self._ciphertext
-        return self.vault.decrypt(self._ciphertext).decode()
+        return to_text(self.vault.decrypt(self._ciphertext))
 
     @data.setter
     def data(self, value):