Sorted set fetch implementation

[bruuuuuuuce]

The sorted set fetch request has been reworked, and updated protos have been merged.

https://github.com/momentohq/client-protos/blob/main/proto/cacheclient.proto#L627-L697

The current impl of sorted set fetch in the rust sdk is now outdated and no longer works. We need to update the implementation to work with the new protos. An up to date impl can be found inside the nodejs sdk https://github.com/momentohq/client-sdk-nodejs/blob/8064043e1782ef8c251773879699698c45a64d79/src/simple-cache-client.ts#L893