chore(sdk): Rust SDK docs for IggyStream API

### Description

Add documentation for the Streaming API of the Rust SDK.
This issue follows previous PRs to add crate level docs:
#3989
#3913
#3809

Add documentation for the following
- modules (mod.rs)
- IggyStream
- IggyStreamConsumer
- IggyStreamProducer
- configs
- traits

Basically everything that lives in
- core/sdk/src/consumer_ext/
- core/sdk/src/stream_builder/

and has a public API.

### Affected area / component

_No response_

### Proposed solution

_No response_

### Alternatives considered

_No response_

### Contribution

- [x] I'm willing to submit a pull request to implement this feature

### Good first issue

- [x] I think this could be a good first issue for a new contributor