This eliminates the need for the FAILURE status codes in
PlanStage and PlanExecutor, and brings query execution's
error reporting more in line with that of the rest of the
server. It also makes it easier for future implementations
of PlanExecutor to comply with the interface.
This commit removes the geoNear command and moves its implementation
into the aggregation framework. Users should use the aggregate command
with a $geoNear stage.
The implementation rewrite additionally removes the limit in the
$geoNear aggregation stage. To limit the number of results, use a $limit
stage.
Addresses the case where a time zone expression lives within a collection
validator as part of a $expr expression. In this case, the Expression
will outlive the OperationContext it was created under.
