refactor(NODE-5514): make FLE logic use async-await

[baileympearson]

Description

What is changing?

To aid in development and debugging of flaky tests, the internals of our FLE logic is now async-await. The notable exception is StateMachine.kmsRequest, which was already manually constructing a promise but is out-of-scope to address now and has a follow up ticket (NODE-3959).

Also note: while I did not refactor kmsRequest to be async itself, I did refactor setTLSOptions to read certificate files asynchronously (in the AC of this ticket).

Along the way, I made a few other cleanups. I commented on which refactors I consider optional and am happy to revert them.

• I made a slight refactor of how we handle kms requests in the state machine (see the comment in the diff view)
• I abstracted mongocryptd respawn logic into a MongocryptdManager.withRespawn helper
• Other misc small changes.

Is there new documentation needed for these changes?

What is the motivation for this change?

Release Highlight

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• 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]

@baileympearson Can we get the conflict resolved and then good to go. Thanks!