[Feature Request] Change Stream support

[AlekSi]

Purpose of the feature.

It would be great if DocumentDB supported Change Streams. That's one of the most requested features in FerretDB: FerretDB/FerretDB#175

Describe the solution you'd like

Change Streams are supported.

Describe alternatives you've considered

Disappoint everyone because of the lack of support for Change Streams.

Additional context

There seem to be some hooks in the current DocumentDB code for Change Streams, so I guess there are some plans to support them.

[lichoil]

it will land second half of this year.