test(NODE-4160): add aws lambda examples

[durran]

Description

Adds examples for using the Node.js driver with AWS Lambda based on the MongoDB examples in the docs here. Note that there is a slight difference in behaviour as the docs add an additional token in the auth mechanism that is not needed, and they only ask for the database name which doesn't actually do anything server side. I've changed here to just list databases in both examples.

Here are the specific tests passing on evg

What is changing?

• Adds a new test/examples directory for the code examples.
• Adds 2 new scripts, check:lambda and check:lambda:aws to run the former with no auth and later with AWS auth.
• Adds 2 example handler functions, handler.js for no auth and aws_handler.js for AWS auth.
• Updates the test readme to mention this new directory.
• Adds 2 new evergreen tasks to run the 2 new scripts in CI

Is there new documentation needed for these changes?

None

What is the motivation for this change?

NODE-4160

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>
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[durran]

Function running in lambda:

[nbbeeken]

LGTM