KIP-1085 — Fix leaking *_DOC variables in StreamsConfig

Accepted Streams

Deprecates several `*_DOC` constants in `StreamsConfig` that have public visibility but are only used internally by `StreamsConfig` or `TopologyConfig`, with a plan to make them private in the next major release. Leaking internal documentation string constants as public API members unnecessarily enlarges the public surface area and risks accidental external usage that would prevent future refactoring.

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