SERVER-13116 distinct isn't sharding aware

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• Backlog

SERVER-42160 $group stages that use a DISTINCT_SCAN do not use a SHARDING_FILTER on sharded collections

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• Backlog

SERVER-5477 when sharded, no need to merge groups if $group _id is the shard key or original document _id

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• Backlog

SERVER-55200 DISTINCT_SCAN not used for $sort+$match+$group+$first on sharded collection

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• Backlog

SERVER-99094 Enable complete $group pushdown for nested pipelines

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• Blocked