Because of parallel tests, which have stalled executions, the RUN
output of a test can be much earlier than its completion output resulting
in hard-to-read verbose output.

The tests are displayed in the order in which the output shows
that they began, to make it easy to line up with the "RUN" output.
Similarly, the definitions of when tests begin and complete is
determined by when RUN and FAIL/SKIP/PASS are output since the
focus of this code is on enhancing readability.

Fixes #19397

Change-Id: I4d0ca3fd268b620484e7a190117f79a33b3dc461
Reviewed-on: https://go-review.googlesource.com/44352
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>