DRIVERS-2469 Add durations to connection pool events

[stIncMale]

This spec change is implemented in https://github.com/mongodb/mongo-java-driver/pull/1166 for the MongoDB Java Driver.

There are no unified tests for CommandSucceededEvent/CommandFailedEvent.duration (see https://github.com/mongodb/specifications/blob/master/source/command-logging-and-monitoring/command-logging-and-monitoring.rst), similarly, there are no unified tests in this PR except those for logging.

DRIVERS-2469

Please complete the following before merging:

• [x] Update changelog.
• [x] Make sure there are generated JSON files from the YAML test files.
• [x] Test changes in at least one language driver.
• [x] Test these changes against all server versions and topologies (including standalone, replica set, sharded clusters, and serverless).

[stIncMale]

A response to https://github.com/mongodb/specifications/pull/1448#pullrequestreview-1570052630 (@baileympearson)

First, we're missing tests for ConnectionCheckoutFailed.duration with the existing tests.

It's here: https://github.com/stIncMale/specifications/blob/DRIVERS-2469/source/connection-monitoring-and-pooling/tests/logging/connection-logging.yml#L216-L224.

Second, the tests currently provide no guarantees about what the fields actually mean. Lastly, the testing strategy relies on logging having been implemented by a driver to test these changes.

Did you consider either trying to add tests to the CMAP unit/integration tests somehow or adding prose tests?

I did. I looked at CommandSucceededEvent/CommandFailedEvent.duration, observed that the only tests for that field is logging tests, and used the same approach, which I also mentioned in the description of the PR. Do you request prose tests for the fields added in this PR?