CDRIVER-5643 Remove cluster time gossiping on SDAM commands

[connorsmacd]

CDRIVER-5643
DRIVERS-2798

Summary

This PR implements a spec change that removes cluster time gossiping on SDAM commands. From the Driver Sessions spec:

Drivers MUST NOT gossip cluster time on SDAM commands. In earlier versions of this spec, drivers did gossip cluster time on SDAM commands, however it was discovered that doing so provides little benefit and can result in a loss of availability. For example, if the driver attempts to connect to a member of a different replica set, the driver can end up with an invalid cluster time. Worse, this invalid cluster time may remain the highest for an indefinite time since clocks between different clusters are not synced. This results in all operations failing until the application is restarted. To fix this issue we decided it was more robust to stop gossiping on SDAM commands altogether.

Changes

• Add a new parameter to mongoc_topology_description_handle_hello to indicate whether or not the cluster time should be updated by the hello.
• Remove cluster_time from mongoc_topology_scanner_t and mongoc_server_monitor_t.
• Update calls to mongoc_topology_description_handle_hello accordingly.
• Add new prose tests.
• Fix existing tests that expected cluster time to be updated by heartbeats.

Testing

There are two new tests for Driver Sessions Prose Test 20: one for single-threaded clients and another for pooled clients. These can be run with:

test-libmongoc -d --no-fork --match "/server_discovery_and_monitoring/monitoring/no_cluster_time/*"

[kevinAlbs]

I like the use of unacknowledged writes to avoid clusterTime updates in the single-threaded test.

[kevinAlbs]

LGTM!