Since test processors create tests dynamically we cannot simply
count how many tests will be run. Instead we count only base tests
that we've loaded, before creating variants.

Bug: v8:6917
Change-Id: Ibc5b9a73f6afad423572afa575f477ca661a99d5
Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/868290
Commit-Queue: Michał Majewski <majeski@google.com>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50642}