Details can be found at SERVER-85213.

This ticket includes any necessary performance investigation and adding additional perf workloads.

Rough idea:

1. In DocumentSourceInternalUnpackBucket::doOptimizeAt(), if it can find $sort followed by $group, then try to optimize
2. If so, then rewrite the $first and/or $last into $top and/or $bottom with the same sort key(s) as the $sort stage. We can use GroupProcessorBase's getMutableAccumulationStatements() to manipulate AccumulationStatement
3. After rewriting, remove the previous $sort stage

This optimization should not be applied when $sort has a limit.

Update:

1. To limit the scope of this ticket and perf impact further, we will apply this optimization only to cases where $_internalUnpackBucket followed by $sort followed by $group.
2. This optimization isn't applied to lastpoint optimizable queries to not regress perf of them.
3. Limit the number of $first and $last only to 2 as a safe limit as overhead of generating the same sort key multiple times for multiple rewritten $top/$bottom could be big if there are too many $first/$last.