Upgrade Node.js to Node 20, the new Active LTS version after 10/24/2023

[justinvp]

Node 20 is becoming the Active LTS version starting October 24th. We should upgrade our images to use that version on or soon after 10/24.

[komalali]

@justinvp bumping this as Node 20 is now LTS

[justinvp]

We now have separate images for 18, 20, and 22: https://hub.docker.com/u/pulumi?page=1&search=pulumi-nodejs. The default image (without suffix) pulumi/pulumi-nodejs still uses 18, but we will start updating this and other languages to track the latest stable version of each language in November.

If you're using the pulumi/pulumi image, you can specify the version of Node.js to use via a .node-version file.

For more details see https://www.pulumi.com/blog/docker-containers