Also create new v8 versions based on the roll ref, which
has some more verification steps than the candidate ref.
Improve bailout regarding existing versions. Only create a
new version if the revisions is in the future.
BUG=chromium:451975
TBR=tandrii@chromium.org
NOTRY=true
LOG=n
Review URL: https://codereview.chromium.org/878913002
Cr-Commit-Position: refs/heads/master@{#26303}
Moved and renamed the scripts to fit with git.
These changes require documentation updates, updates of
the release spreadsheet and the buildbot side.
BUG=chromium:451975
TBR=tandrii@chromium.org
NOTRY=true
LOG=n
Review URL: https://codereview.chromium.org/868473004
Cr-Commit-Position: refs/heads/master@{#26271}
