Add debug data to help diagnose HTTP2 test failure (dotnet/corefx#38345)

Add debug data to help diagnose HTTP2 test failure (dotnet/corefx#38345)

The GoAwayFrame_AbortAllPendingStreams_StreamFailWithExpectedException test has been frequently hanging on some Linux distros.  This adds some diagnostics to help track it down in CI: every minute, it'll dump out the fields of the async state machine, which if nothing else will let us see which await it's stuck on and what is the state of each of the tasks.

Commit migrated from https://github.com/dotnet/corefx/commit/410a162f68eb319e8066ac7bf2d7bcd6e2ce47d0