Add new expressions for date: https://docs.google.com/document/d/1mrnRdlXUgFMFIzGuO7c6Vkx9TurNkKjbqCXoSEOQO_A/edit#
https://docs.google.com/document/d/1zgvfbgD4ergTpA3BzOeWmHeGcDGC3ZBQUUrL95PuxYc/edit#heading=h.b1os3ai9s8t3

Add new window function stage and relevant accumulators:
https://docs.google.com/document/d/1IDbgaoEN9ttB9DNPk5mbRIT6S935QaL0HKlKGwOcSHE/edit#heading=h.gjhbqspr3hb9

The following keywords are related to the $setWindowFields stage: $count, $derivative, $integral, $covariancePop, $covarianceSamp, $expMovingAvg, $shift, $documentNumber, $rank, $denseRank

$count can be used in $group too.

Currently, we do not have the logic in place to show only relevant keywords for the stage. We check only for a supported version.