Description of your changes

As discussed in #1191, AWS Lambda announced support for the nodejs18.x runtime a few weeks ago. This PR introduces the changes necessary to run unit and integration tests on the new runtime, as well as changing the default Node version used for development to Node.js 18.

How to verify this change

See checks under the PR (unit tests) as well as result of integration tests (link to run in the comments below).

Related issues, RFCs

Issue number: #1191

PR status

Is this ready for review?: YES
Is it a breaking change?: NO

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding changes to the examples
• My changes generate no new warnings
• The code coverage hasn't decreased
• I have added tests that prove my change is effective and works
• New and existing unit tests pass locally and in Github Actions
• Any dependent changes have been merged and published
• The PR title follows the conventional commit semantics

Breaking change checklist

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.