Add support for pymongo 4.x

[vtomasr5]

Relates to https://github.com/closeio/closeio/issues/34125

To officially support MongoDB 6.0+ we need to upgrade to pymongo 4+.

The upstream mongoengine added support for Pymongo 4 in version (0.24+). The PR.

[wojcikstefan]

This was done. See:

• Add Python v3.11 to the test matrix #48
• Run tests on MongoDB v5.0.23 instead of v3.2.19 #49
• Add MongoDB 6.0.19 to the test matrix #50
• Use list_collection_names vs collection_names #51
• Use command-based createUser vs Database.add_user #52
• Use command-based profile vs Database.set_profiling_level #54
• Remove db.authenticate #58
• Use MongoClient vs MongoReplicaSetClient #59
• uuidrepresentation defaults to PYTHON_LEGACY #60
• Use update_one instead of update #61
• Refactor count to count_documents and estimated_document_count #62
• Bump requirements.txt pymongo 3.12.3 -> 4.2.0 #64