redis: include local property on Lock class (#6083)

The Lock class as a property local that has a token property that sometimes
needs be accessed / set.

```python
lock = redis.lock(key)
lock.local.token = token
lock.extend(10)
```

Technically the type of `local` is `SimpleNamespace | threading.local`
but I think this setup is a bit stricter but satisfies the API.

stubs/redis/redis/lock.pyi

@@ -1,11 +1,16 @@
 from types import TracebackType
 from typing import Any, Text, Type, Union
+from typing_extensions import Protocol
 
 from redis.client import Redis
 
 _TokenValue = Union[bytes, Text]
 
+class _Local(Protocol):
+    token: _TokenValue | None
+
 class Lock:
+    local: _Local
     def __init__(
         self,
         redis: Redis[Any],