This moves to node 22 and debian bookworm, since the versions we've been building and testing with are getting old.
There is some old material kept around for (speaks very quietly) Python 2 (looks around hoping no-one heard) which we continue to support for some long-time users but really really should drop soon.
The changes for the node upgrade were all test related. I did them in a way that shouldn't impair running on older versions of node, and did spot checks for this. This is to give some breathing room for upgrading Grist Lab's grist-saas as follow up work.
