feature: Support nio `async.it` tests

[MisanthropicBit]

1. Extend the custom output handler to check the path of each test. If it matches the nio.tests module, mark it with a thirdPartyAsync: true field in the json output.
2. Since we cannot reliably parse the stacktrace from busted/lua, extract the test's parent, likely its describe block (also appears to handle top-level async.it calls), and put that in the json output as well.
3. If a test is marked with thirdPartyAsync: true then find its parent in the tree and find the child that corresponds to the async.it test using the neotestPositionId key in the json output and associate the test with it.