Ending Support For Node 14 and Node 16 in November 2023

[dangowans]

More and more dependencies are dropping support for Node 14 and Node 16 since both versions have reached end-of-life.

In November 2023, this project will follow suit, stop testing against these older versions of Node, and fully embrace Node 18 and Node 20.

• Update engines block in package.json to >=18.0.0.
• Unblock dependency updates that discontinue support for Node 14 and Node 16.
• Remove helpers/polyfills as they are no longer needed.
• Update Node versions in coverage.yml.

[dangowans]

Updated in acabebe