[FIX][ENTERPRISE] Engagement Dashboard displaying incorrect data about active users (#22381)

* Fix data grouping, labels and dates in the Engagement Dashboard

* Fix DAU, WAU and MAU values in Active Users chart

* Fix previous values for WAU, MAU, DAU and timezone in Busiest Chat Time section

* Add engagement-dashboard/users/active-users endpoint to endpoint.ts file

* Add date to tooltip (active users chart)

* Add support to UTC timezone

Co-authored-by: Tasso Evangelista <tasso.evangelista@rocket.chat>