Mask value if the key is token (apache#16474)

Some connections (including the databricks connection) use the key 'token' in the 'extra' field (this has always been the case). Including it here so that these sensitive tokens are also masked by default.

The prior implementation just masked all of the 'extra' json: "XXXXXXXX" if conn.extra_dejson else None https://github.com/apache/airflow/blob/88199eefccb4c805f8d6527bab5bf600b397c35e/airflow/hooks/base.py#L78

(cherry picked from commit d1d04fe)
(cherry picked from commit 24f3f63)

airflow/utils/log/secrets_masker.py

@@ -55,6 +55,7 @@
         'password',
         'private_key',
         'secret',
+        'token',
     }
 )
 """Names of fields (Connection extra, Variable key name etc.) that are deemed sensitive"""