Epic: Upgrade to Node.js 20

[benfrancis]

Node.js 10 has now been end of life for a long time and is starting to be unsupported in a lot of dependencies of the gateway.

We have been stuck on an old Node version due to a dependence on Raspbian Buster on existing installations, which can't be automatically upgraded. When we migrate to a new base OS with automatic OTA updates in 2.0, I'm hoping we can upgrade to Node.js 20 (the current LTS release).

See also: #3031