test(NODE-6631): Implement integration tests for improved client.close() - sockets + timers

[aditi-khare-mongoDB]

Description

Add socket integration tests for client.close().

What is changing?

• Assert socket creation and clean-up through libuv tracking for each relevant driver instance of socket creation.
• Assert timer creation by asserting timers are defined on relevant client components and assert timer clean-up through process.getActiveResourceInfo()
  • Timer existence is more finicky to test, and require some artificial delaying of promises and high timer MSs
  • ex: a high heartbeatFrequencyMS to ensure we're not in between intervals when we assert MonitorInterval's timer exits

To see more information regarding testing plan outline see the design document, specifically the dropdowns under Sockets and Timers sections, respectively.

Is there new documentation needed for these changes?

No

What is the motivation for this change?

Improved client.close()

Release Highlight

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[evergreen-ci-prod]

There is an existing patch(es) for this commit SHA:

• Evergreen patch with PR

Please note that the status that is posted is not in the context of this PR but rather the (latest) existing patch and that may affect some tests that may depend on the particular PR. If your tests do not rely on any PR-specific values (like base or head branch name) then your tests will report the same status. If you would like a patch to run in the context of this PR and abort the other(s), comment 'evergreen retry'.

[aditi-khare-mongoDB]

Follow-up from NODE-6620: We do want to clean up inactive sockets

[aditi-khare-mongoDB]

See the note on the comment. This test has a higher chance of being flaky since the client can't set minPoolSizeCheckFrequencyMS. I can this to set the variable to a higher value using sinon if preferred by reviewers.