`infected_asyncio` task hang (`SIGINT` ignored!) on debug mode breakpointing?

[goodboy]

As found in d6ed97d0 of the #351 work, there is a nasty issue that causes an un-interrupt-able hang when we use enough tractor.breakpoint()s in the right spots and infected asyncio mode where the asyncio task somehow gets stuck in some kind of cancelled state (maybe?)

The whole thing needs to be more thoroughly investigated and a proper test suite built out.

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ToDo testing:

• [ ] at least one test that actually uses the flags intro-ed in d6ed97d0 with a comparable timeout.
  • [ ] a fix for that case ^ :joy: