feat(adapter/kv): support async iterating on scan results

[PragmaTwice]

Which issue does this PR close?

Closes #3639.

Rationale for this change

Instead of performing a full scanning and returning a Vec<String>, now we introduce an associated type into kv::Adapter:

type Scanner: Scan;

So that the implementation can do paged scanning and returns a ScanIter, and users can iterate over it to get keys in batches from the server.

What changes are included in this PR?

• add associated type ScanIter into kv::Adapter and refactor KvLister and Adaptor's Accessor impl;
• refactor all services using kv::Adapter, especially for which has list cap;
• for sqlite (via sqlx): now, instead of using fetch_all, we can use fetch to fetch data in batches instead of fetching all data.

Are there any user-facing changes?

No changes for end users.

[Xuanwo]

There are some critical bug fixes that need to be released. I will merge this after we create a new release.