node 20: ava fails in node 18.19.0

[josephjclark]

Node 18.18.2 is absolutely fine.

Node 18.19.0 breaks ava.

What's happening SOMEHOW is the ts-node esm loader, which we use to run our ava tests, breaks against the very latest node. At least for the worker-threaded approach (forcing ava to run with child processes works fine).

I think we SHOULD be using @ava/typescript and not ts-node/esm to handle the typescript tests. But @ava/typescript fails for me, even in a minimal testing project, and I can't work it out. See #541 for notes on that.

The build, so far as I can tell, is unaffected.

As a wider note our node version is quickly drifting out of date and we really ought to get on a 20x version (if not 21 soon). I wonder too if we should run our integration test suite against LTS 18 and 20 as well as the latest node build - just to ensure stability.