SERVER-32016 Create an interruptible class/data structure that handles serializing operations per namespace

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• Closed

SERVER-56654 Do not use the collection distributed lock for chunk splits

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• Closed

SERVER-56779 Do not use the collection distributed lock for chunk merges

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• Closed

SERVER-30148 Move force primary refresh functionality out of the ShardServerCatalogCacheLoader into the ShardingState's refresh logic

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• Closed

SERVER-62162 Complete TODO listed in SERVER-25359

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• Closed