new feature: support key-based rate limit

### Feature Description

Hi team, in production usage we've found hot key impacting storage service (the classic hotspotting issue for distributed system). I'm wondering apart from server-side support, if it's possible to add hotkey rate limit at client side as well, so we could
- reduce IO request proactively before service overloads
- 429 Too Many Requests is usually considered retriable, which could worsen production environment further (see https://github.com/apache/opendal/issues/7376 as well)

### Problem and Solution

I'm wondering if we could add key-based rate limit, one viable data structure could be [count-min sketch](https://en.wikipedia.org/wiki/Count%E2%80%93min_sketch).

### Additional Context

_No response_

### Are you willing to contribute to the development of this feature?

- [ ] Yes, I am willing to contribute to the development of this feature.

The issue names no files, tests, or entry points. Start by reviewing the client-side rate-limit design and the proposed count-min sketch approach; done would require an agreed key-based limit and implementation scope.

Written by the indexing model from the issue text.