Enhance Experience Buffer Processing Pipeline

[pan-x-c]

In order to

1. handle complex multi-round interaction experiences,
2. reduce the functional overlap between existing buffer-related modules,
3. avoid dependency conflicts with data-juicer,

We propose to refactor the experience data processor module, and the following is the specific plan:

1. Add Operator interface, allowing users to implement this interface to process experience data in a pipeline manner.
2. Add ExperienceProcessor actor, responsible for continuously running operators.
3. Merge AddStrategy and SampleStrategy into Operator to avoid functional overlap.
4. Optimize Data-Juicer service call method to avoid dependency conflicts.
5. Add Operator developer guideline to guide users on how to write their own Operators.

We plan to implement the above features in about two weeks and release Trinity-RFT v0.3.0