Using test generators meant that we had to remove the progress indicator since
the total number of tests weren't known before-hand.

This CL implements a progress indicator using test number estimations.

cctest and unittests progress indicator is accurate, however estimating
means the progress will terminate over 100% in big test suites and sometimes
under 100%.

R=machenbach@chromium.org
CC=​sergiyb@chromium.org,yangguo@chromium.org

Bug: v8:8769
Change-Id: I40ca5b40f9b1223376d33707f0945900ea98cea3
Reviewed-on: https://chromium-review.googlesource.com/c/1460471
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59538}