Make the Zstd Codec use the Context Singletons
Make the Zstd Codec use the Context Singletons

Summary: Use pre-existing cached local contexts, rather than creating our own.

Reviewed By: bimbashrestha

Differential Revision: D18890550

fbshipit-source-id: d53d0bdf35ebfcfa5dfb45da6b99a886022d5f8b

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