Code structure refactor

[hnyls2002]

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Motivation

To make the components of SRT more organized.

Modification

1. Rename: manager_single, manager_multi to controller_xxx
2. Make a module model_executor and move all model execution logic into this.
3. (Next PR) Make a cache abstraction.
4. (Next PR) Organize infer_batch and input_metadata, make infer_batch only for scheduling and intpu_metadata for model forward.

Checklist

1. Ensure pre-commit pre-commit run --all-files or other linting tools are used to fix potential lint issues.
2. Confirm that modifications are covered by complete unit tests. If not, please add more unit tests for correctness.
3. Modify documentation as needed, such as docstrings or example tutorials.