[hack] Add new language_feature_logging option to .hhconfig options
[hack] Add new language_feature_logging option to .hhconfig options

Summary: The stats associated with different implementation of lambdas used to piggy-back on the `sharedmem_log_level` control in `.hhconfig`. This was accidentally broken in a previous diff. Now we separate these stats from the shared-memory info, using a new option `language_feature_logging` in `.hhconfig`. At the same time, logging of basic GC info is always enabled (major_collections, major_words, etc.).

Reviewed By: oulgen

Differential Revision: D7498586

fbshipit-source-id: 9d701c76d1faf50836249f431bfc174ba82c3c3d

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