[release] 1.0.1rc1: more logs and defensive mechanism for test collection

[zhming0]

We had one report of Test Result upload contains empty data. User claimed that this only started happening since v1.0.0.

I couldn't not reproduce the same issue (using the same pytest version) so I had to make a logical guess:

• The fact that upload works means our plugin is successfully loaded.
• The fact that v0.2.0 works means there is no problem in our pytest_runtest_logreport hook (v1 introduced pytest_runtest_teardown hook to collect test, v0.2 relies solely on pytest_runtest_logreport).
• So my guess is that something prevent pytest_runtest_teardown from running.

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So I added lots of debug logging, user can opt-in to seeing them by setting env var DEBUG=1.

I also add some a defensive mechanism: another pytest_runtest_logfinish hook hoping as a fallback option.