pymongo should be an optional requirement #20259
Description
The pymongo driver is installed by default, but as the number of IO connectors in the python sdk grows, I don't think this is the precedent we want to set. We already have "extra" packages for gcp, aws, and interactive, we should also add one for mongo.
Imported from Jira BEAM-9626. Original Jira may contain additional context.
Reported by: chadrik.