fix(NODE-4863): do not use RetryableWriteError for non-server errors

[alenakhineika]

Description

Use the MongoErrorLabel.PoolRequstedRetry label instead of misused MongoErrorLabel.RetryableWriteError for non-server errors according to spec.

What is changing?

• The PoolClearedError constructor adds the new MongoErrorLabel.PoolRequstedRetry label instead of misused MongoErrorLabel.RetryableWriteError.
• The isRetryableWriteError function checks if PoolRequstedRetry or RetryableWriteError is set to determine if retryOperation is required.

Is there new documentation needed for these changes?

None

What is the motivation for this change?

NODE-4863

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

[durran]

Just notes for other reviewers, the testing requirements made it seem to me like the prose test #2 should change somehow, but checking the spec this test matches so no change actually needed there.

The second testing requirement I'm not sure where that came from but I think the additional unit test added here suffices.