`scan` for redis service

## Wanted feature

The `Operator` built from `Redis` could use `scan` to `list` entries matching the [glob-style pattern of redis](https://redis.io/commands/keys/).

## Real scene

There is a function called **move registration** in our system. Users register via the function where the uploading file should be move to after its transmission done. Every registration record has its own ID (`move_id`), and every file also has its own ID (`meta_id`). Then we format them into `movreg_{move_id}_{meta_id}` as the key in redis.

We may have only one of the two IDs to query the value. For example, we have only meta_id `832917` and it was stored as `movreg_432432_832917`; to get the value, we need to excute:

```redis
> keys movreg_*_832917
"movreg_432432_832917"

> get movreg_432432_832917
```

That's why we need glob-style scan in opendal; we want to get all the value whose key matches the given pattern.

## Conjectures about implementation

I think `KEYS` or `SCAN` can work. Both of them could do glob-match on whole database. But `KEYS` is slower in general.

Start by tracing the Operator built from Redis and the existing Redis key and value operations. Compare the requested glob-style lookup with Redis SCAN and KEYS semantics, then determine how matching entries should be exposed. Done means callers can query Redis values using patterns such as movreg_*_832917.

Written by the indexing model from the issue text.