Test cp313t in CI

[lysnikolaou]

• This adds building wheels for cp313t in CI.
• Also adds config for running the test suite under 3.13t. (this will probably fail due to the pycurl and pycares dependencies for now)

[bdarnell]

What's the status of this? Are you waiting for me? It looks like the last build run at https://github.com/lysnikolaou/tornado/actions failed so I've been waiting for an update or a new build to show up there.

[lysnikolaou]

I'm sorry about the delay here. I had an initial look at the failures when they first happened, but then got busy with other stuff and didn't make time for this.

The failures seem to be pointing to real thread-safety issues in Python. It is very odd that they happen when everything runs in a single thread though, so I'll have to dive deeper before I can give you more information. I plan to do so next week or the week after.

[bdarnell]

No worries, take your time. I just wanted to make sure you weren't waiting on me and had successful test runs that I hadn't seen.

[lysnikolaou]

Closing this in favor of #3525.