Support chunked prefill when radix cache is disabled

[hnyls2002]

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Motivation

Make cache an abstract class, which is more convenient for other types of caches than radix cache.

Modification

• abstraction
• chunked prefill cache

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.