Frequency partitioning and FOR encoding rebased & synced with nimble/main#636

David-C-L wants to merge 30 commits intofacebookincubator:mainfacebookincubator/nimble:mainfrom

David-C-L:freq-part-and-for-syncedDavid-C-L/nimble-new-encodings-fork:freq-part-and-for-syncedCopy head branch name to clipboard