redis key_formatter should handle cases where client keys contain hash tag

*Title*: *redis key_formatter should handle cases where client keys contain hash tag*

*Description*:
Redis supports hash tag feature which can be used to to take a curly braces wrapped substring for key hash.
Consider a scenario where user specify a key_formatter that uses hash tag, e.g. `prefix-{%KEY%}`, and the client key contains hash tag as well, e.g. `foo-{bar}`. The formatted key becomes `prefix-{foo-{bar}}` and `foo-{bar` will be used for hash instead of`bar` intended by client.
The proposed change is to add an option for key_formatter to prefer client key's hash tag if present. If the feature is enabled and the first pair of curly braces in key_formatter wraps %KEY% which also contains hash tag, the key_formatter will be stripped off of the pair of curly braces. In the above example, the formatted key becomes `prefix-foo-{bar}`.

[optional *Relevant Links*:]
[redis hash tag](https://redis.io/docs/reference/cluster-spec/#:~:text=Hash-,tags,-There%20is%20an)