unstructured

51cf6bf7 - rfctr(chunking): extract strategy-specific chunking options (#2556)

rfctr(chunking): extract strategy-specific chunking options (#2556) **Summary** A pluggable chunking strategy needs its own local set of chunking options that subclasses a base-class in `unstructured`. Extract distinct `_ByTitleChunkingOptions` and `_BasicChunkingOptions` for the existing two chunking strategies and move their strategy-specific option setting and validation to the respective subclass. This was also a good opportunity for us to clean up a few odds and ends we'd been meaning to. Might be worth looking at the commits individually as they are cohesive incremental steps toward the goal.