refactor: move CountDocument logic into collection API

[nbbeeken]

Description

What is changing?

• Delete CountDocument operation class
• Move logic into collection.countDocuments

Is there new documentation needed for these changes?

What is the motivation for this change?

The subclass is unneccessary and make typing difficult. See: #4112 (comment)

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

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[nbbeeken]

This should merge to main as a PR separate from the cursor response changes, it currently targets the cursor response PR because it relies on changes in there.

[nbbeeken]

#4148