Make sure 0rtt works as expected

[rklaehn]

We should have some test to make sure 0rtt works as expected, either patchbay or otherwise. IIRC there were some changes that might influence 0rtt, and 0rtt is essential for some of the things I want to do with iroh.

[rklaehn]

0rtt does work as expected. There are some rare corner cases where the NEW_TOKEN mechanism is needed to get the full benefit of 0rtt, which is currently impossible because the client side token log is not reused between connections.

Bugfix is here: #4317

But that is unrelated to 0rtt as such.